Agent skill · posthog
profiling-slow-api-endpoints
Profiles slow PostHog API endpoints when the main cost is in Postgres or Python. Use when a screen, picker, or list is slow; a Django endpoint has high tail latency; a query plan changes with tenant size; or a proposed database fix needs production evidence. Covers APM traces, safe production EXPLAIN, representative measurements, implementation choices, tests, rollout, and post-deploy verification. For ClickHouse or HogQL latency, use `optimizing-clickhouse-and-hogql-queries` instead.
What it needs
About 3k tokens when loaded.
What this skill does
Profiling slow API endpoints Use this skill when a PostHog API request spends most of its time in Postgres or Python. For ClickHouse and HogQL, use optimizing-clickhouse-and-hogql-queries. Measure the same user action before and after the change. A faster query does not help if the action stays slow. Find the source of the delay Record the page action, endpoint, request shape, affected users, request volume, and a latency percentile such as p95. Read slow APM traces with posthog:query-apm-spans and the exploring-apm-traces skill. The distribution shows how often requests are slow. The traces show where they spend time. Django ORM and cursor.execute spans point to Postgres. ClickHouse work belongs in the ClickHouse skill. Time outside database spans can indicate repeated calls, serialization, or excess data loading. Follow the request to the function that creates the work. Do not optimize a view wrapper when another function owns the delay. Capture the exact work Get the SQL and parameters from a slow request. Keep its filters, ordering, and page size. Check for repeated queries, count queries, and work that does not block the response. A reduced query can use a different plan. Local data and statistics can also produce a different plan. Use querying-production-databases-via-metabase to inspect the production read replica. Start with EXPLAIN. Use EXPLAIN (ANALYZE, BUFFERS) only when the exact SELECT is safe to run. Inspect row estimates, indexes, join types, loops, filters, sorts, and buffer use. Compare the smallest useful change Remove work that the response does not need before you change a query or add an index. Compare the original and candidate with the same parameters. Run each more than once, record the cache state, and verify equal results. Measure the tenant-size distribution when plans can change with tenant size. Test both sides of a plan crossover before you select a threshold. One tenant is not enough evidence for a conditional plan. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills posthog/profiling-slow-api-endpoints