Performance Optimize Litt Keymap Pebble Options

[Kbhat1]

• Open LittDB's default pebble keymap with options sized for its workload: 64MB memtable, compaction concurrency scaling to 8, and per-level bloom filters
• Vs using stock empty &pebble.Options{}

[cursor]

PR Summary

Medium Risk
Changes core storage engine tuning for the keymap path; behavior is unchanged but compaction/memory tradeoffs could affect node performance or disk use under load.

Overview
Litt PebbleDBKeymap now opens Pebble with workload-specific options instead of default &pebble.Options{}, targeting high-rate batched writes and point lookups (e.g. hash keys).

The new keymapPebbleOptions() sets a 64MB memtable, higher L0 / stop-write thresholds, compaction concurrency up to 8, and per-level bloom filters for lookup-heavy reads. Intent is to reduce memtable churn, L0 backlog, and write stalls under sustained keymap traffic.

A TestKeymapPebbleOptions test locks in memtable size, compaction upper bound, and bloom filters so reverting to stock options would fail CI.

^{Reviewed by Cursor Bugbot for commit 50f9639. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Jun 16, 2026, 2:56 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.09%. Comparing base (d5f544a) to head (50f9639).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3594      +/-   ##
==========================================
- Coverage   58.97%   58.09%   -0.89%     
==========================================
  Files        2208     2134      -74     
  Lines      181744   173210    -8534     
==========================================
- Hits       107180   100619    -6561     
+ Misses      64938    63665    -1273     
+ Partials     9626     8926     -700     

Flag	Coverage Δ
sei-chain-pr	69.74% <100.00%> (?)
sei-db	70.41% <ø> (ø)
sei-db-state-db	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...b_engine/litt/disktable/keymap/pebble_db_keymap.go	64.42% <100.00%> (+5.08%)	⬆️

... and 74 files with indirect coverage changes

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