diff --git a/.coveragerc b/.coveragerc
index 011b38b..b1b560b 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1,10 +1,29 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 [run]
 source = BTrees
 # New in 5.0; required for the GHA coveralls submission.
 relative_files = True
+branch = true
+
+[paths]
+source =
+    src/
+    .tox/*/lib/python*/site-packages/
+    .tox/pypy*/site-packages/
 
 [report]
+show_missing = true
+precision = 2
 exclude_lines =
+    except ImportError:
+    if __name__ == '__main__':
     pragma: no cover
-    class I[A-Z]\w+\((Interface|I[A-Z].*)\):
-    self.fail
+    pragma: nocover
+    raise AssertionError
+    raise NotImplementedError
+    raise unittest.Skip
+    self.fail\(
+
+[html]
+directory = parts/htmlcov
diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..9d3c4f2
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,39 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
+#
+# EditorConfig Configuration file, for more details see:
+# http://EditorConfig.org
+# EditorConfig is a convention description, that could be interpreted
+# by multiple editors to enforce common coding conventions for specific
+# file types
+
+# top-most EditorConfig file:
+# Will ignore other EditorConfig files in Home directory or upper tree level.
+root = true
+
+
+[*]  # For All Files
+# Unix-style newlines with a newline ending every file
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+# Set default charset
+charset = utf-8
+# Indent style default
+indent_style = space
+# Max Line Length - a hard line wrap, should be disabled
+max_line_length = off
+
+[*.{py,cfg,ini}]
+# 4 space indentation
+indent_size = 4
+
+[*.{yml,zpt,pt,dtml,zcml}]
+# 2 space indentation
+indent_size = 2
+
+[{Makefile,.gitmodules}]
+# Tab indentation (no size specified, but view as 4 spaces)
+indent_style = tab
+indent_size = unset
+tab_width = unset
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 707e9fe..aa03952 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -1,7 +1,9 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 ###
 # Initially copied from
 # https://github.com/actions/starter-workflows/blob/main/ci/python-package.yml
-# And later based on the version I (jamadden) updated at
+# And later based on the version jamadden updated at
 # gevent/gevent, and then at zodb/relstorage and zodb/perfmetrics
 #
 # Original comment follows.
@@ -35,14 +37,14 @@
 name: tests
 
 
-# Triggers the workflow on push or pull request events
-on: [push, pull_request, workflow_dispatch]
-# Limiting to particular branches might be helpful to conserve minutes.
-#on:
-  # push:
-  #   branches: [ $default-branch ]
-  # pull_request:
-  #   branches: [ $default-branch ]
+# Triggers the workflow on push or pull request events and periodically
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '0 12 * * 0'  # run once a week on Sunday
+  # Allow to run this workflow manually from the Actions tab
+  workflow_dispatch:
 
 env:
   # Weirdly, this has to be a top-level key, not ``defaults.env``
@@ -52,12 +54,6 @@ env:
   PYTHONDEVMODE: 1
   PYTHONFAULTHANDLER: 1
   ZOPE_INTERFACE_STRICT_IRO: 1
-  ZOPE_INTERFACE_LOG_CHANGED_IRO: 1
-  # Require C extensions; this will be disabled later for
-  # PyPy because zope.interface through at least 5.3
-  # tries to import its C module even on PyPy with this, but
-  # the wheels tend not to have it.
-  PURE_PYTHON: 0
 
   PIP_UPGRADE_STRATEGY: eager
   # Don't get warnings about Python 2 support being deprecated. We
@@ -74,11 +70,10 @@ env:
 
   ###
   # caching
-  # This is where we'd set up ccache
+  # This is where we'd set up ccache, but this compiles so fast its not worth it.
   ###
 
 
-
 jobs:
   # Because sharing code/steps is so hard, and because it can be
   # extremely valuable to be able to get binary wheels without
@@ -92,21 +87,31 @@ jobs:
   # This division is time-saving for projects that take awhile to
   # build, but somewhat less of a clear-cut win given how quick this
   # is to compile (at least at this writing).
-  build-BTrees:
+  build-package:
     # Sigh. Note that the matrix must be kept in sync
     # with `test`, and `docs` must use a subset.
     runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
-        python-version: [2.7, pypy-2.7, pypy-3.6, 3.5, 3.6, 3.7, 3.8, 3.9]
+        python-version:
+          - "2.7"
+          - "3.5"
+          - "pypy-2.7"
+          - "pypy-3.7"
+          - "3.6"
+          - "3.7"
+          - "3.8"
+          - "3.9"
+          - "3.10"
         os: [ubuntu-20.04, macos-latest]
         exclude:
           - os: macos-latest
-            python-version: pypy-2.7
+            python-version: "pypy-2.7"
           - os: macos-latest
-            python-version: pypy-3.6
+            python-version: "pypy-3.7"
           - os: macos-latest
-            python-version: 3.5
+            python-version: "3.5"
 
     steps:
       - name: checkout
@@ -137,13 +142,7 @@ jobs:
       - name: Install Build Dependencies
         run: |
           pip install -U pip
-          pip install -U setuptools wheel twine
-          pip install -U coveralls coverage persistent
-
-      - name: Set pure Python
-        if: ${{ startsWith(matrix.python-version, 'pypy') }}
-        run: |
-          echo PURE_PYTHON=1 >> $GITHUB_ENV
+          pip install -U setuptools wheel twine cffi
 
       - name: Build BTrees
         run: |
@@ -152,9 +151,8 @@ jobs:
           python setup.py build_ext -i
           python setup.py bdist_wheel
           # Also install it, so that we get dependencies in the (pip) cache.
-          pip install -U coverage
           pip install -U 'faulthandler; python_version == "2.7" and platform_python_implementation == "CPython"'
-          pip install .[test,ZODB]
+          pip install .[test]
 
       - name: Check BTrees build
         run: |
@@ -169,26 +167,40 @@ jobs:
         # We cannot 'uses: pypa/gh-action-pypi-publish@v1.4.1' because
         # that's apparently a container action, and those don't run on
         # the Mac.
-        if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags') && startsWith(runner.os, 'Mac')
+        if: >
+          github.event_name == 'push'
+          && startsWith(github.ref, 'refs/tags')
+          && startsWith(runner.os, 'Mac')
+          && !startsWith(matrix.python-version, 'pypy')
         env:
           TWINE_PASSWORD: ${{ secrets.TWINE_PASSWORD }}
         run: |
           twine upload --skip-existing dist/*
 
   test:
-    needs: build-BTrees
+    needs: build-package
     runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
-        python-version: [2.7, pypy-2.7, pypy-3.6, 3.5, 3.6, 3.7, 3.8, 3.9]
+        python-version:
+          - "2.7"
+          - "3.5"
+          - "pypy-2.7"
+          - "pypy-3.7"
+          - "3.6"
+          - "3.7"
+          - "3.8"
+          - "3.9"
+          - "3.10"
         os: [ubuntu-20.04, macos-latest]
         exclude:
           - os: macos-latest
-            python-version: pypy-2.7
+            python-version: "pypy-2.7"
           - os: macos-latest
-            python-version: pypy-3.6
+            python-version: "pypy-3.7"
           - os: macos-latest
-            python-version: 3.5
+            python-version: "3.5"
 
     steps:
       - name: checkout
@@ -197,6 +209,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      ###
+      # Caching.
+      # This actually *restores* a cache and schedules a cleanup action
+      # to save the cache. So it must come before the thing we want to use
+      # the cache.
+      ###
       - name: Get pip cache dir
         id: pip-cache
         run: |
@@ -209,10 +227,6 @@ jobs:
           key: ${{ runner.os }}-pip-${{ matrix.python-version }}
           restore-keys: |
             ${{ runner.os }}-pip-
-      - name: Set pure Python
-        if: ${{ startsWith(matrix.python-version, 'pypy') }}
-        run: |
-          echo PURE_PYTHON=1 >> $GITHUB_ENV
 
       - name: Download BTrees wheel
         uses: actions/download-artifact@v2
@@ -220,45 +234,27 @@ jobs:
           name: BTrees-${{ runner.os }}-${{ matrix.python-version }}.whl
           path: dist/
       - name: Install BTrees
-        # ``python -m unittest discover`` only works with editable
-        # installs, so we have to duplicate some work and can't
-        # install the built wheel. (zope.testrunner
-        # works fine with non-editable installs.)
         run: |
-          ls -l dist
-          ls -l .
-          pip install -U wheel
+          pip install -U wheel setuptools
           pip install -U coverage
           pip install -U 'faulthandler; python_version == "2.7" and platform_python_implementation == "CPython"'
           # Unzip into src/ so that testrunner can find the .so files
           # when we ask it to load tests from that directory. This
           # might also save some build time?
           unzip -n dist/BTrees-*whl -d src
-          pip install -U -e .[test,ZODB]
-      - name: Set coverage status
-        # coverage is too slow on PyPy. We can't submit it from macOS (see that action),
-        # so don't bother taking the speed hit there either.
-        if: ${{ !startsWith(matrix.python-version, 'pypy') && startsWith(runner.os, 'Linux') }}
-        run: |
-          echo WITH_COVERAGE=1 >> $GITHUB_ENV
-      - name: Run native tests
-        # Here, run natively just once. Only run PURE_PYTHON
-        # again once, because these tests take awhile, and PURE_PYTHON
-        # runs once under PyPy anyway (but with coverage takes forever).
+          pip install -U -e .[test]
+      - name: Run tests with C extensions
+        if: ${{ !startsWith(matrix.python-version, 'pypy') }}
         run: |
-          if [[ "$WITH_COVERAGE" == "1" ]]; then
-              coverage run -p -m unittest discover -s src
-          else
-              python -m unittest discover -s src
-          fi
-      - name: Run PURE_PYTHON tests
-        if: (matrix.python-version == 2.7 || matrix.python-version == 3.9) && startsWith(runner.os, 'Linux')
+          python -m coverage run -p -m zope.testrunner --test-path=src --auto-color --auto-progress
+      - name: Run tests without C extensions
+        run:
+          # coverage makes PyPy run about 3x slower!
+          PURE_PYTHON=1 python -m coverage run -p -m zope.testrunner --test-path=src --auto-color --auto-progress
+      - name: Report Coverage
         run: |
-          PURE_PYTHON=1 coverage run -p -m unittest discover -s src
-      - name: Report coverage
-        run: |
-          coverage combine || true
-          coverage report -i || true
+          coverage combine
+          coverage report -i
       - name: Submit to Coveralls
         # This is a container action, which only runs on Linux.
         if: ${{ startsWith(runner.os, 'Linux') }}
@@ -276,11 +272,11 @@ jobs:
         parallel-finished: true
 
   docs:
-    needs: build-BTrees
+    needs: build-package
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [3.9]
+        python-version: ["3.9"]
         os: [ubuntu-20.04]
 
     steps:
@@ -290,6 +286,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      ###
+      # Caching.
+      # This actually *restores* a cache and schedules a cleanup action
+      # to save the cache. So it must come before the thing we want to use
+      # the cache.
+      ###
       - name: Get pip cache dir
         id: pip-cache
         run: |
@@ -312,22 +314,20 @@ jobs:
         run: |
           pip install -U wheel
           pip install -U coverage
-          pip install -U 'faulthandler; python_version == "2.7" and platform_python_implementation == "CPython"'
           pip install -U  "`ls dist/BTrees-*.whl`[docs]"
       - name: Build docs
         env:
-          ZOPE_INTERFACE_STRICT_IRO: 0
+          ZOPE_INTERFACE_STRICT_IRO: 1
         run: |
           sphinx-build -b html -d docs/_build/doctrees docs docs/_build/html
           sphinx-build -b doctest -d docs/_build/doctrees docs docs/_build/doctest
 
-
   lint:
-    needs: build-BTrees
+    needs: build-package
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [3.9]
+        python-version: ["3.9"]
         os: [ubuntu-20.04]
 
     steps:
@@ -337,7 +337,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
-
+      ###
+      # Caching.
+      # This actually *restores* a cache and schedules a cleanup action
+      # to save the cache. So it must come before the thing we want to use
+      # the cache.
+      ###
       - name: Get pip cache dir
         id: pip-cache
         run: |
@@ -360,7 +365,7 @@ jobs:
         run: |
           pip install -U pip
           pip install -U wheel
-          pip install -U `ls dist/BTrees-*`[test,ZODB]
+          pip install -U `ls dist/BTrees-*`[test]
       - name: Lint
         # We only need to do this on one version, and it should be Python 3, because
         # pylint has stopped updating for Python 2.
@@ -374,7 +379,7 @@ jobs:
     # We use a regular Python matrix entry to share as much code as possible.
     strategy:
       matrix:
-        python-version: [3.9]
+        python-version: ["3.9"]
         image: [manylinux2010_x86_64, manylinux2010_i686, manylinux2014_aarch64]
 
     steps:
@@ -384,6 +389,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      ###
+      # Caching.
+      # This actually *restores* a cache and schedules a cleanup action
+      # to save the cache. So it must come before the thing we want to use
+      # the cache.
+      ###
       - name: Get pip cache dir
         id: pip-cache
         run: |
@@ -407,13 +418,13 @@ jobs:
         # The 2010 image is the most recent spec that comes with Python 2.7,
         # and only up through the tag 2021-02-06-3d322a5
         env:
-          DOCKER_IMAGE: quay.io/pypa/${{ matrix.image }}:2021-02-06-3d322a5
+          DOCKER_IMAGE: quay.io/pypa/${{ matrix.image }}
         run: |
           bash .manylinux.sh
       - name: Build BTrees (i686)
         if: matrix.image == 'manylinux2010_i686'
         env:
-          DOCKER_IMAGE: quay.io/pypa/${{ matrix.image }}:2021-02-06-3d322a5
+          DOCKER_IMAGE: quay.io/pypa/${{ matrix.image }}
           PRE_CMD: linux32
         run: |
           bash .manylinux.sh
@@ -435,22 +446,11 @@ jobs:
         run: sudo chown -R $(whoami) ${{ steps.pip-cache.outputs.dir }}
       - name: Publish package to PyPI
         uses: pypa/gh-action-pypi-publish@v1.4.1
-        if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags')
+        if: >
+          github.event_name == 'push'
+          && startsWith(github.ref, 'refs/tags')
         with:
           user: __token__
           password: ${{ secrets.TWINE_PASSWORD }}
           skip_existing: true
           packages_dir: wheelhouse/
-
-# TODO:
-# * Use YAML syntax to share snippets, like the old .travis.yml did
-# Sadly, as of 2021-02-01, Github Actions does not support anchors at
-# all. Just having an anchor results in an error:
-#
-#   The workflow is not valid. .github/workflows/tests.yml: Anchors
-#   are not currently supported. Remove the anchor 'an-strategy'
-#
-# The alternative of using composite actions doesn't work either,
-# because composite actions are limited to running shell scripts.
-# Steps in them can't call other actions with `uses:`, and nor can
-# they be conditional with `if:`.
diff --git a/.gitignore b/.gitignore
index 315b87d..20b2128 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,21 +1,31 @@
-bin
-eggs
-develop-eggs
-parts
-.installed.cfg
-build
-docs/_build
-__pycache__
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
+*.dll
+*.egg-info/
+*.profraw
 *.pyc
+*.pyo
 *.so
-.tox
 .coverage
-nosetests.xml
-coverage.xml
-*.egg-info
-*.egg
-dist
+.coverage.*
 .eggs/
-.dir-locals.el
-pip-wheel-metadata/
-htmlcov/
+.installed.cfg
+.mr.developer.cfg
+.tox/
+.vscode/
+__pycache__/
+bin/
+build/
+coverage.xml
+develop-eggs/
+develop/
+dist/
+docs/_build
+eggs/
+etc/
+lib/
+lib64
+log/
+parts/
+pyvenv.cfg
+var/
diff --git a/.manylinux-install.sh b/.manylinux-install.sh
index e5bef77..e1921f1 100755
--- a/.manylinux-install.sh
+++ b/.manylinux-install.sh
@@ -1,4 +1,6 @@
 #!/usr/bin/env bash
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 
 set -e -x
 
@@ -33,33 +35,47 @@ else
 fi
 
 export PURE_PYTHON=0
+# https://wiki.centos.org/yum-errors suggests this might help against yum
+# errors:
+yum clean all
+rm -rf /var/cache/yum/*
+# We need some libraries because we build wheels from scratch:
+yum -y install libffi-devel
 
 # Compile wheels
-cd /io/
-for variant in `ls -d /opt/python/cp{27,36,37,38,39}*`; do
-    PYBIN="$variant/bin"
-    "${PYBIN}/pip" install persistent wheel setuptools
-    "${PYBIN}/python" setup.py bdist_wheel
-    ls dist
-    if [ `uname -m` == 'aarch64' ]; then
-        # Running the test suite takes forever in
-        # emulation; an early run (using tox, which is also slow)
-        # took over an hour to build and then run the 2.7 tests and move on
-        # to the 3.5 tests. We still want to run tests, though!
-        # We don't want to distribute wheels for a platform that's
-        # completely untested. Consequently, we limit it to running
-        # in just one interpreter, the newest one on the list (which in principle
-        # should be the fastest), and we don't install the ZODB extra.
-        if [[ "${PYBIN}" == *"cp39"* ]]; then
-            "${PYBIN}/pip" install -e .[test]
-            "${PYBIN}/python" -c 'import BTrees.OOBTree; print(BTrees.OOBTree.BTree, BTrees.OOBTree.BTreePy)'
-            "${PYBIN}/python" -m unittest discover -s src
+for PYBIN in /opt/python/*/bin; do
+    if \
+       [[ "${PYBIN}" == *"cp27"* ]] || \
+       [[ "${PYBIN}" == *"cp35"* ]] || \
+       [[ "${PYBIN}" == *"cp36"* ]] || \
+       [[ "${PYBIN}" == *"cp37"* ]] || \
+       [[ "${PYBIN}" == *"cp38"* ]] || \
+       [[ "${PYBIN}" == *"cp39"* ]] || \
+       [[ "${PYBIN}" == *"cp310"* ]] ; then
+        "${PYBIN}/pip" install -e /io/
+        "${PYBIN}/pip" wheel /io/ -w wheelhouse/
+        if [ `uname -m` == 'aarch64' ]; then
+          # Running the test suite takes forever in
+          # emulation; an early run (using tox, which is also slow)
+          # took over an hour to build and then run the 2.7 tests and move on
+          # to the 3.5 tests. We still want to run tests, though!
+          # We don't want to distribute wheels for a platform that's
+          # completely untested. Consequently, we limit it to running
+          # in just one interpreter, the newest one on the list (which in principle
+          # should be the fastest), and we don't install the ZODB extra.
+          if [[ "${PYBIN}" == *"cp39"* ]]; then
+              cd /io/
+              "${PYBIN}/pip" install -e .[test]
+              "${PYBIN}/python" -c 'import BTrees.OOBTree; print(BTrees.OOBTree.BTree, BTrees.OOBTree.BTreePy)'
+              "${PYBIN}/python" -m unittest discover -s src
+              cd ..
+          fi
         fi
+        rm -rf /io/build /io/*.egg-info
     fi
-    rm -rf /io/build /io/*.egg-info
 done
 
 # Bundle external shared libraries into the wheels
-for whl in dist/BTrees*.whl; do
+for whl in wheelhouse/BTrees*.whl; do
     auditwheel repair "$whl" -w /io/wheelhouse/
 done
diff --git a/.manylinux.sh b/.manylinux.sh
index 520d68e..ea4ef41 100755
--- a/.manylinux.sh
+++ b/.manylinux.sh
@@ -1,4 +1,6 @@
 #!/usr/bin/env bash
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 
 set -e -x
 
diff --git a/.meta.toml b/.meta.toml
new file mode 100644
index 0000000..6e4b6bb
--- /dev/null
+++ b/.meta.toml
@@ -0,0 +1,98 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
+[meta]
+template = "c-code"
+commit-id = "1b2a5eb60d5b2b3fcee16692b0a9a6a26172c06a"
+
+[python]
+with-appveyor = true
+with-windows = false
+with-pypy = true
+with-future-python = false
+with-legacy-python = true
+with-docs = true
+with-sphinx-doctests = true
+
+[tox]
+use-flake8 = false
+additional-envlist = [
+    "w_zodb",
+    "w_zodb-pure",
+    ]
+testenv-setenv = [
+    "PYTHONFAULTHANDLER=1",
+    "PYTHONDEVMODE=1",
+    "ZOPE_INTERFACE_STRICT_IRO=1",
+    "ZOPE_INTERFACE_LOG_CHANGED_IRO=1",
+    ]
+testenv-additional = [
+    "",
+    "[testenv:w_zodb]",
+    "basepython = python3.9",
+    "deps = ZODB",
+    "",
+    "[testenv:w_zodb-pure]",
+    "basepython = python3.9",
+    "deps = ZODB",
+    ]
+
+[coverage]
+fail-under = 93
+
+[manifest]
+additional-rules = [
+    "include *.sh",
+    "recursive-include docs *.bat",
+    "recursive-include docs *.css",
+    "recursive-include src *.c",
+    "recursive-include src *.h",
+    ]
+
+[check-manifest]
+additional-ignores = [
+    "docs/_build/html/_static/*",
+    "docs/_build/html/_static/*/*",
+    ]
+
+[appveyor]
+global-env-vars = [
+    "# Currently the builds use @mgedmin's Appveyor account.  The PyPI token belongs",
+    "# to zope.wheelbuilder, which is managed by @mgedmin and @dataflake.",
+    "global:",
+    "  TWINE_USERNAME: __token__",
+    "  TWINE_PASSWORD:",
+    "    secure: aoZC/+rvJKg8B5GMGIxd1a+XrG6uK7c37/wnoeA74KlRM9aqyayAnJxNyzyAAsCNzdLl7gz6wEC7lq/oYd3Rcb8mcK+K2U1mqbeG3SeIigCWLKtTnAK9EUiuaVGKVrKvywY7Ckp1uBh5To7PQn5ZS6QEe7YvJODljrGc8O2Z3TjofUzwE28L7P89BgZwCr+/3oOXsY3DHZXUGGYcIjkczLXoDsZ+X9/1WWbVdoTkgeXZmVQbl/a9nYilXILOh2NQtJLn0cInPZyPLfdGw88ZWw==",
+    ]
+
+[c-code]
+manylinux-install-setup = [
+    "export CFLAGS=\"-pipe\"",
+    "if [ `uname -m` == 'aarch64' ]; then",
+    "    # Compiling with -Ofast on the arm emulator takes hours. The default settings have -O3,",
+    "    # and adding -Os doesn't help much; -O1 seems too.",
+    "    echo \"Compiling with -O1\"",
+    "    export CFLAGS=\"-O1 $CFLAGS\"",
+    "else",
+    "    echo \"Compiling with -Ofast\"",
+    "    export CFLAGS=\"-Ofast $CFLAGS\"",
+    "fi",
+    "",
+    "export PURE_PYTHON=0",
+    ]
+manylinux-aarch64-tests = [
+    "# Running the test suite takes forever in",
+    "# emulation; an early run (using tox, which is also slow)",
+    "# took over an hour to build and then run the 2.7 tests and move on",
+    "# to the 3.5 tests. We still want to run tests, though!",
+    "# We don't want to distribute wheels for a platform that's",
+    "# completely untested. Consequently, we limit it to running",
+    "# in just one interpreter, the newest one on the list (which in principle",
+    "# should be the fastest), and we don't install the ZODB extra.",
+    "if [[ \"${PYBIN}\" == *\"cp39\"* ]]; then",
+    "    cd /io/",
+    "    \"${PYBIN}/pip\" install -e .[test]",
+    "    \"${PYBIN}/python\" -c 'import BTrees.OOBTree; print(BTrees.OOBTree.BTree, BTrees.OOBTree.BTreePy)'",
+    "    \"${PYBIN}/python\" -m unittest discover -s src",
+    "    cd ..",
+    "fi",
+    ]
diff --git a/CHANGES.rst b/CHANGES.rst
index 725f2b4..ac9f756 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -2,10 +2,10 @@
  BTrees Changelog
 ==================
 
-4.9.3 (unreleased)
-==================
+4.10.0 (unreleased)
+===================
 
-- Nothing changed yet.
+- Add support for Python 3.10.
 
 
 4.9.2 (2021-06-09)
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..e6d84b8
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,23 @@
+<!--
+Generated from:
+https://github.com/zopefoundation/meta/tree/master/config/c-code
+--> 
+# Contributing to zopefoundation projects
+
+The projects under the zopefoundation GitHub organization are open source and
+welcome contributions in different forms:
+
+* bug reports
+* code improvements and bug fixes
+* documentation improvements
+* pull request reviews
+
+For any changes in the repository besides trivial typo fixes you are required
+to sign the contributor agreement. See
+https://www.zope.dev/developer/becoming-a-committer.html for details.
+
+Please visit our [Developer
+Guidelines](https://www.zope.dev/developer/guidelines.html) if you'd like to
+contribute code changes and our [guidelines for reporting
+bugs](https://www.zope.dev/developer/reporting-bugs.html) if you want to file a
+bug report.
diff --git a/MANIFEST.in b/MANIFEST.in
index b98bba5..dd97482 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,22 +1,21 @@
-include pyproject.toml
-
-include *.txt
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
+include *.md
 include *.rst
-include *.py
+include *.txt
 include buildout.cfg
 include tox.ini
+include appveyor.yml
 include .coveragerc
 
-recursive-include docs *
-recursive-include src *
-recursive-include .github *
-
-global-exclude *.dll
-global-exclude *.pyc
-global-exclude *.pyo
-global-exclude *.so
-global-exclude *~
-global-exclude *\#
-global-exclude coverage.xml
+recursive-include docs *.py
+recursive-include docs *.rst
+recursive-include docs *.txt
+recursive-include docs Makefile
 
-prune docs/_build
+recursive-include src *.py
+include *.sh
+recursive-include docs *.bat
+recursive-include docs *.css
+recursive-include src *.c
+recursive-include src *.h
diff --git a/appveyor.yml b/appveyor.yml
index 30380dc..ae937ab 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,7 +1,8 @@
-# Currently the builds use @mgedmin's Appveyor account.  The PyPI token belongs
-# to zope.wheelbuilder, which is managed by @mgedmin and @dataflake.
-
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 environment:
+  # Currently the builds use @mgedmin's Appveyor account.  The PyPI token belongs
+  # to zope.wheelbuilder, which is managed by @mgedmin and @dataflake.
   global:
     TWINE_USERNAME: __token__
     TWINE_PASSWORD:
@@ -20,8 +21,11 @@ environment:
     - python: 38-x64
     - python: 39
     - python: 39-x64
+    - python: 310
+    - python: 310-x64
 
 install:
+  - "SET PYTHONVERSION=%PYTHON%"
   - "SET PATH=C:\\Python%PYTHON%;c:\\Python%PYTHON%\\scripts;%PATH%"
   - ps: |
       $env:PYTHON = "C:\\Python${env:PYTHON}"
@@ -31,21 +35,23 @@ install:
       }
   - ps: if (-not (Test-Path $env:PYTHON)) { throw "No $env:PYTHON" }
   - echo "C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\SetEnv.cmd" /x64 > "C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin\amd64\vcvars64.bat"
-  - pip install -e .[test,ZODB]
+  - python -m pip install -U pip
+  - pip install -U setuptools wheel
+  - pip install -U -e .[test]
+
+matrix:
+  fast_finish: true
 
 build_script:
-  - python -m pip install -U pip
-  - pip install wheel
   - python -W ignore setup.py -q bdist_wheel
 
 test_script:
   - zope-testrunner --test-path=src
-
 artifacts:
   - path: 'dist\*.whl'
     name: wheel
 
 deploy_script:
-  - ps: if ($env:APPVEYOR_REPO_TAG -eq $TRUE) { pip install twine; twine upload --skip-existing dist/* }
+  - ps: if ($env:APPVEYOR_REPO_TAG -eq $TRUE) { pip install twine; twine upload --skip-existing dist\*.whl }
 
 deploy: on
diff --git a/bootstrap.py b/bootstrap.py
deleted file mode 100644
index a459921..0000000
--- a/bootstrap.py
+++ /dev/null
@@ -1,210 +0,0 @@
-##############################################################################
-#
-# Copyright (c) 2006 Zope Foundation and Contributors.
-# All Rights Reserved.
-#
-# This software is subject to the provisions of the Zope Public License,
-# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
-# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
-# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
-# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
-# FOR A PARTICULAR PURPOSE.
-#
-##############################################################################
-"""Bootstrap a buildout-based project
-
-Simply run this script in a directory containing a buildout.cfg.
-The script accepts buildout command-line options, so you can
-use the -c option to specify an alternate configuration file.
-"""
-
-import os
-import shutil
-import sys
-import tempfile
-
-from optparse import OptionParser
-
-__version__ = '2015-07-01'
-# See zc.buildout's changelog if this version is up to date.
-
-tmpeggs = tempfile.mkdtemp(prefix='bootstrap-')
-
-usage = '''\
-[DESIRED PYTHON FOR BUILDOUT] bootstrap.py [options]
-
-Bootstraps a buildout-based project.
-
-Simply run this script in a directory containing a buildout.cfg, using the
-Python that you want bin/buildout to use.
-
-Note that by using --find-links to point to local resources, you can keep
-this script from going over the network.
-'''
-
-parser = OptionParser(usage=usage)
-parser.add_option("--version",
-                  action="store_true", default=False,
-                  help=("Return bootstrap.py version."))
-parser.add_option("-t", "--accept-buildout-test-releases",
-                  dest='accept_buildout_test_releases',
-                  action="store_true", default=False,
-                  help=("Normally, if you do not specify a --version, the "
-                        "bootstrap script and buildout gets the newest "
-                        "*final* versions of zc.buildout and its recipes and "
-                        "extensions for you.  If you use this flag, "
-                        "bootstrap and buildout will get the newest releases "
-                        "even if they are alphas or betas."))
-parser.add_option("-c", "--config-file",
-                  help=("Specify the path to the buildout configuration "
-                        "file to be used."))
-parser.add_option("-f", "--find-links",
-                  help=("Specify a URL to search for buildout releases"))
-parser.add_option("--allow-site-packages",
-                  action="store_true", default=False,
-                  help=("Let bootstrap.py use existing site packages"))
-parser.add_option("--buildout-version",
-                  help="Use a specific zc.buildout version")
-parser.add_option("--setuptools-version",
-                  help="Use a specific setuptools version")
-parser.add_option("--setuptools-to-dir",
-                  help=("Allow for re-use of existing directory of "
-                        "setuptools versions"))
-
-options, args = parser.parse_args()
-if options.version:
-    print("bootstrap.py version %s" % __version__)
-    sys.exit(0)
-
-
-######################################################################
-# load/install setuptools
-
-try:
-    from urllib.request import urlopen
-except ImportError:
-    from urllib2 import urlopen
-
-ez = {}
-if os.path.exists('ez_setup.py'):
-    exec(open('ez_setup.py').read(), ez)
-else:
-    exec(urlopen('https://bootstrap.pypa.io/ez_setup.py').read(), ez)
-
-if not options.allow_site_packages:
-    # ez_setup imports site, which adds site packages
-    # this will remove them from the path to ensure that incompatible versions
-    # of setuptools are not in the path
-    import site
-    # inside a virtualenv, there is no 'getsitepackages'.
-    # We can't remove these reliably
-    if hasattr(site, 'getsitepackages'):
-        for sitepackage_path in site.getsitepackages():
-            # Strip all site-packages directories from sys.path that
-            # are not sys.prefix; this is because on Windows
-            # sys.prefix is a site-package directory.
-            if sitepackage_path != sys.prefix:
-                sys.path[:] = [x for x in sys.path
-                               if sitepackage_path not in x]
-
-setup_args = dict(to_dir=tmpeggs, download_delay=0)
-
-if options.setuptools_version is not None:
-    setup_args['version'] = options.setuptools_version
-if options.setuptools_to_dir is not None:
-    setup_args['to_dir'] = options.setuptools_to_dir
-
-ez['use_setuptools'](**setup_args)
-import setuptools
-import pkg_resources
-
-# This does not (always?) update the default working set.  We will
-# do it.
-for path in sys.path:
-    if path not in pkg_resources.working_set.entries:
-        pkg_resources.working_set.add_entry(path)
-
-######################################################################
-# Install buildout
-
-ws = pkg_resources.working_set
-
-setuptools_path = ws.find(
-    pkg_resources.Requirement.parse('setuptools')).location
-
-# Fix sys.path here as easy_install.pth added before PYTHONPATH
-cmd = [sys.executable, '-c',
-       'import sys; sys.path[0:0] = [%r]; ' % setuptools_path +
-       'from setuptools.command.easy_install import main; main()',
-       '-mZqNxd', tmpeggs]
-
-find_links = os.environ.get(
-    'bootstrap-testing-find-links',
-    options.find_links or
-    ('http://downloads.buildout.org/'
-     if options.accept_buildout_test_releases else None)
-    )
-if find_links:
-    cmd.extend(['-f', find_links])
-
-requirement = 'zc.buildout'
-version = options.buildout_version
-if version is None and not options.accept_buildout_test_releases:
-    # Figure out the most recent final version of zc.buildout.
-    import setuptools.package_index
-    _final_parts = '*final-', '*final'
-
-    def _final_version(parsed_version):
-        try:
-            return not parsed_version.is_prerelease
-        except AttributeError:
-            # Older setuptools
-            for part in parsed_version:
-                if (part[:1] == '*') and (part not in _final_parts):
-                    return False
-            return True
-
-    index = setuptools.package_index.PackageIndex(
-        search_path=[setuptools_path])
-    if find_links:
-        index.add_find_links((find_links,))
-    req = pkg_resources.Requirement.parse(requirement)
-    if index.obtain(req) is not None:
-        best = []
-        bestv = None
-        for dist in index[req.project_name]:
-            distv = dist.parsed_version
-            if _final_version(distv):
-                if bestv is None or distv > bestv:
-                    best = [dist]
-                    bestv = distv
-                elif distv == bestv:
-                    best.append(dist)
-        if best:
-            best.sort()
-            version = best[-1].version
-if version:
-    requirement = '=='.join((requirement, version))
-cmd.append(requirement)
-
-import subprocess
-if subprocess.call(cmd) != 0:
-    raise Exception(
-        "Failed to execute command:\n%s" % repr(cmd)[1:-1])
-
-######################################################################
-# Import and run buildout
-
-ws.add_entry(tmpeggs)
-ws.require(requirement)
-import zc.buildout.buildout
-
-if not [a for a in args if '=' not in a]:
-    args.append('bootstrap')
-
-# if -c was provided, we push it back into args for buildout' main function
-if options.config_file is not None:
-    args[0:0] = ['-c', options.config_file]
-
-zc.buildout.buildout.main(args)
-shutil.rmtree(tmpeggs)
diff --git a/docs/overview.rst b/docs/overview.rst
index 8540254..21ecc93 100644
--- a/docs/overview.rst
+++ b/docs/overview.rst
@@ -141,7 +141,7 @@ exclusive of the range's endpoints.
    'green'
    >>> s = t.keys() # this is a "lazy" sequence object
    >>> s
-   <OOBTreeItems object at ...>
+   <...TreeItems object at ...>
    >>> len(s)  # it acts like a Python list
    4
    >>> s[-2]
@@ -260,9 +260,10 @@ example, lists supply a total ordering, and then
    >>> L2[0] = 5                # horrible -- the set is insane now
    >>> s.has_key([3])           # for example, it's insane this way
    False
-   >>> s
-   OOSet([[1], [5], [3]])
-   >>>
+   >>> s.__class__
+   <class 'BTrees.OOBTree.OOSet'>
+   >>> list(s)
+   [[1], [5], [3]]
 
 Key lookup relies on that the keys remain in sorted order (an efficient form of
 binary search is used).  By mutating key L2 after inserting it, we destroyed the
diff --git a/setup.cfg b/setup.cfg
index 1da15c1..9d8b94c 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,24 +1,19 @@
-[nosetests]
-nocapture=1
-cover-package=BTrees
-cover-erase=1
-cover-branches=1
-cover-min-percentage=100
-with-doctest=0
-where=BTrees
-
-[aliases]
-dev = develop easy_install BTrees[testing]
-docs = develop easy_install BTrees[docs]
-
-[check-manifest]
-ignore =
-    .manylinux-install.sh
-    .manylinux.sh
-    appveyor.yml
-
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 [bdist_wheel]
-universal = 0
+universal = 1
 
 [zest.releaser]
 create-wheel = no
+
+[flake8]
+doctests = 1
+
+[check-manifest]
+ignore =
+    .editorconfig
+    .meta.toml
+    docs/_build/html/_sources/*
+    docs/_build/doctest/*
+    docs/_build/html/_static/*
+    docs/_build/html/_static/*/*
diff --git a/setup.py b/setup.py
index a413cdf..9d7488f 100644
--- a/setup.py
+++ b/setup.py
@@ -25,7 +25,7 @@
 from setuptools import setup
 from setuptools.command.build_ext import build_ext
 
-version = '4.9.3.dev0'
+version = '4.10.0.dev0'
 
 def _read(fname):
     here = os.path.abspath(os.path.dirname(__file__))
@@ -197,6 +197,7 @@ def BTreeExtension(family):
           "Programming Language :: Python :: 3.7",
           "Programming Language :: Python :: 3.8",
           "Programming Language :: Python :: 3.9",
+          "Programming Language :: Python :: 3.10",
           "Programming Language :: Python :: Implementation :: CPython",
           "Programming Language :: Python :: Implementation :: PyPy",
           "Framework :: ZODB",
@@ -222,8 +223,7 @@ def BTreeExtension(family):
               'ZODB',
           ],
           'docs': [
-              # Sphinx 4 and r.s.autointerface 0.8 are incompatible.
-              'Sphinx < 4',
+              'Sphinx',
               'repoze.sphinx.autointerface',
               'sphinx_rtd_theme',
           ],
diff --git a/src/BTrees/_base.py b/src/BTrees/_base.py
index 0f9f4f8..8a3b278 100644
--- a/src/BTrees/_base.py
+++ b/src/BTrees/_base.py
@@ -995,8 +995,7 @@ def has_key(self, key):
         index = self._search(key)
         if index < 0:
             return False
-        r = self._data[index].child.has_key(key)
-        return r and r + 1
+        return self._data[index].child.has_key(key)
 
     def keys(self, min=_marker, max=_marker,
              excludemin=False, excludemax=False,
diff --git a/tox.ini b/tox.ini
index c96598a..afbf9df 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,59 +1,77 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 [tox]
+minversion = 3.18
 envlist =
-# Jython support pending 2.7 support, due 2012-07-15 or so.  See:
-# http://fwierzbicki.blogspot.com/2012/03/adconion-to-fund-jython-27.html
-#   py27,jython,pypy,coverage,docs
-    py27,py27-pure,py35,py35-pure,py36,py37,py38,py39,pypy,pypy3,w_zodb,w_zodb-pure,coverage,docs
+    lint
+    py27,py27-pure
+    py35,py35-pure
+    py36,py36-pure
+    py37,py37-pure
+    py38,py38-pure
+    py39,py39-pure
+    py310,py310-pure
+    pypy
+    pypy3
+    docs
+    coverage
+    w_zodb
+    w_zodb-pure
 
 [testenv]
 usedevelop = true
-extras =
-    test
-commands =
-    python -m zope.testrunner --test-path=src --auto-color --auto-progress {posargs}
+deps =
 setenv =
+    pure: PURE_PYTHON=1
+    !pure-!pypy-!pypy3: PURE_PYTHON=0
     PYTHONFAULTHANDLER=1
     PYTHONDEVMODE=1
     ZOPE_INTERFACE_STRICT_IRO=1
     ZOPE_INTERFACE_LOG_CHANGED_IRO=1
-    PURE_PYTHON=0
-    pure: PURE_PYTHON=1
-    pypy: PURE_PYTHON=1
-    pypy3: PURE_PYTHON=1
-
-#[testenv:jython]
-#commands =
-#   jython setup.py test -q
+commands =
+    zope-testrunner --test-path=src {posargs:-vc}
+    !py27-!pypy: sphinx-build -b doctest -d {envdir}/.cache/doctrees docs {envdir}/.cache/doctest
+extras =
+    test
+    docs
 
 [testenv:w_zodb]
-basepython =
-    python2.7
-deps =
-    ZODB
+basepython = python3.9
+deps = ZODB
 
 [testenv:w_zodb-pure]
-basepython =
-    python2.7
-deps =
-    ZODB
+basepython = python3.9
+deps = ZODB
 
 [testenv:coverage]
-basepython =
-    python3
-commands =
-    coverage run -m zope.testrunner --test-path=src --auto-color --auto-progress {posargs}
-    coverage report --fail-under=92
+basepython = python3
+allowlist_externals =
+    mkdir
 deps =
     coverage
-    ZODB
+setenv =
+    PURE_PYTHON=1
+commands =
+    mkdir -p {toxinidir}/parts/htmlcov
+    coverage run -m zope.testrunner --test-path=src {posargs:-vc}
+    coverage html -i
+    coverage report -i -m --fail-under=93
+
+[testenv:lint]
+basepython = python3
+skip_install = true
+deps =
+    check-manifest
+    check-python-versions >= 0.19.1
+    wheel
+commands =
+    check-manifest
+    check-python-versions
 
 [testenv:docs]
-basepython =
-    python3
+basepython = python3
+skip_install = false
+commands_pre =
 commands =
     sphinx-build -b html -d docs/_build/doctrees docs docs/_build/html
     sphinx-build -b doctest -d docs/_build/doctrees docs docs/_build/doctest
-deps =
-    --requirement doc-requirements.txt
-extras =
-    docs