#rails

Databases Bug Report

Deep pages taking seconds with OFFSET pagination, fixed with keyset cursors

Daniel Tran · Jan 13, 2026 · 8 min read

Page 1 of our activity feed loaded in 9 ms, page 4,000 in 3.2 seconds, and a partner's sync job was walking every page. OFFSET makes Postgres read and discard every earlier row. We switched to keyset pagination with a tie-breaker and a matching index.

Databases Bug Report

MySQL deadlock on concurrent INSERT ... ON DUPLICATE KEY UPDATE batches

Daniel Tran · Nov 26, 2024 · 9 min read

Stock updates from supplier feeds started failing with Deadlock found when trying to get lock during peak hours. Concurrent upsert batches touched the same unique keys in different orders under InnoDB next-key locking. Sorting, smaller batches and a retry fixed it.