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Rails Performance: Query Plans, Cache, and Queue Latency

Guides for Rails performance work that starts with evidence: query plans, cache behavior, queue latency, time-series growth, and deploy cost checks. The useful question is not "how do we make Rails faster"; it is which measured path is slow, expensive, or fragile enough to change.

SLOW PAGE OR REPORT

Start with request traces, query count, `pg_stat_statements`, and the worst `EXPLAIN ANALYZE` plan before adding a cache.

CACHE CHURN OR REDIS COST

Use the Solid Cache guide only after measuring hit rate, write churn, object size, and PostgreSQL headroom.

GROWING EVENT DATA

TimescaleDB is worth considering when retention, compression, and time-bucket aggregates are already database work.

QUEUE LATENCY

Use Mission Control and queue metrics before changing workers. Separate stuck jobs, retry storms, and ordinary throughput pressure.

Bad Fit For This Hub

Do not start here if the problem is only "the app feels slow" and nobody can name the affected page, job, report, or API path. First collect one trace, one slow query list, queue latency, cache hit-rate data, or the business path users are waiting on. Without that evidence, performance work turns into guesswork.

Need a Rails performance audit?

Performance work starts at the query log, the slow-query table, and the three worst query plans, not at a caching layer. Show me the endpoint or job users actually feel and the `pg_stat_statements` rows behind it, and the profiling points at the real fix: a query, an index, a cache boundary, a job split, or more capacity. If the fix turns out to be removing Redis, the Rails 8 Solid Stack hub covers that path.

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