Notes & Learnings

Writing

Field notes from building and scaling production systems — AI engineering, backend practice, database internals, and system design, written to be the reference I wish I'd had.

Incident notes: sargability, EXPLAIN ANALYZE, and the retry loop that made it worse

DatabaseAug 9, 20268 min read

I Had the Index. My Query Was Still Timing Out.

A Postgres RPC with the exact right index still threw 57014 statement timeouts at 1.4M calls a day. The index was fine — the predicate wrapped the column in arithmetic and made it unusable.

PostgreSQLIndexingPerformanceProduction Incident

AI EngineeringJul 2, 20268 min read

Your RAG System Is Lying to You: Index Questions, Not Chunks

Standard RAG returned the wrong page with a confident 0.753 score. A version that scored lower — 0.694 — returned the right one. Here's RAG's silent failure mode, why similarity scores can't be trusted, and the fix I shipped as QIndex.

RAGEmbeddingsRetrievalOpen Source