• POST /db/train: train zstd compression dictionaries for the repos, blocks, and events keyspaces. dictionaries are written to disk; a restart is required to apply them. the crawler, firehose, and backfill worker are paused for the duration and restored on completion.
• POST /db/compact: trigger a full major compaction of all database keyspaces in parallel. the crawler, firehose, and backfill worker are paused for the duration and restored on completion.