diff --git a/.github/workflows/run_tests_CI.yml b/.github/workflows/run_tests_CI.yml
index 0cc7d72eb..8b6157fd1 100644
--- a/.github/workflows/run_tests_CI.yml
+++ b/.github/workflows/run_tests_CI.yml
@@ -27,7 +27,7 @@ jobs:
           - Gemfile
           - Gemfile.next
         ruby:
-          - 2.6
+          - 2.7
         spec-commands:
           - 'spec/controllers/api/v1/[a-m]*.rb spec/counters spec/operations spec/serializers spec/workers'
           - 'spec/controllers/api/v1/[n-s]*.rb'
diff --git a/Dockerfile b/Dockerfile
index 2e388f65a..b6695ec2c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,4 @@
-# debian stretch has libjemalloc1 https://packages.debian.org/stretch/libjemalloc1
-FROM ruby:2.6-slim-stretch
+FROM ruby:2.7-slim
 
 WORKDIR /rails_app
 
@@ -8,15 +7,19 @@ RUN apt-get update && apt-get -y upgrade && \
         build-essential \
         # git is required for installing gems from git repos
         git \
-        # libjemalloc1 (v3) provides big memory savings vs jemalloc v5+ (default on debian buster)
-        libjemalloc1 \
+        # install jemalloc (v5) for memory savings
+        libjemalloc2 \
         libpq-dev \
         nodejs \
         tmpreaper \
         && \
         apt-get clean
 
-ENV LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.1
+# configure jemalloc v5 with v3 behaviours (trade ram usage over performance)
+# https://twitter.com/nateberkopec/status/1442894624935137288
+# https://github.com/code-dot-org/code-dot-org/blob/5c8b24674d1c2f7e51e85dd32124e113dc423d84/cookbooks/cdo-jemalloc/attributes/default.rb#L10
+ENV MALLOC_CONF="narenas:2,background_thread:true,thp:never,dirty_decay_ms:1000,muzzy_decay_ms:0"
+ENV LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.2
 
 # set a default RAILS_ENV for the build scripts
 # this is required for the `rake assets:precompile` script
@@ -28,6 +31,7 @@ ADD ./Gemfile /rails_app/
 ADD ./Gemfile.lock /rails_app/
 
 RUN bundle config --global jobs `cat /proc/cpuinfo | grep processor | wc -l | xargs -I % expr % - 1`
+RUN gem update --system
 RUN bundle install --without development test
 
 ADD ./ /rails_app
diff --git a/Dockerfile.dev b/Dockerfile.dev
index 43b0490a4..d32b626ac 100644
--- a/Dockerfile.dev
+++ b/Dockerfile.dev
@@ -1,4 +1,4 @@
-FROM ruby:2.6-slim-buster
+FROM ruby:2.7-slim-buster
 
 WORKDIR /rails_app
 
@@ -8,14 +8,18 @@ RUN apt-get update && apt-get -y upgrade && \
       # git is required for installing gems from git repos
       git \
       libpq-dev \
-      # debian buster has v11 by default
+      # debian buster and comes with pg client v11 by default
       postgresql-client-11 \
       tmpreaper
 
+# set MRI memory allocator to mimic jemalloc memory savings
+ENV MALLOC_ARENA_MAX=2
+
 ADD ./Gemfile /rails_app/
 ADD ./Gemfile.lock /rails_app/
 
 RUN bundle config --global jobs `cat /proc/cpuinfo | grep processor | wc -l | xargs -I % expr % - 1`
+RUN gem update --system
 RUN bundle install
 
 ADD ./ /rails_app