AI Weekly Malaysia

Tailscale traced a series of outages starting August 2025 to a 16-year-old bug in SQLite's write-ahead log checkpointing process. After a six-month investigation, SQLite maintainers had to build a new VFS activity logging tool (funded by Tailscale) just to reproduce the issue, which resisted all initial debugging attempts. Tailscale has used SQLite as its primary database since 2022, and the corruption first surfaced during their routine snapshot-to-S3 backup pipeline.

Why: If you ship SQLite in production with WAL mode and periodic snapshot backups, this postmortem is a direct warning that WAL checkpoint corruption can surface silently and be extremely hard to reproduce. Database learners and builders should read the Tailscale write-up before assuming SQLite's WAL is bulletproof in backup-heavy workloads, and consider whether their own backup pipeline could hit the same edge case now that the bug is documented.

Tailscale experienced 19 separate SQLite database corruption incidents over six months, traced to a 16-year-old WAL-reset bug deep in SQLite. Their architecture uses one SQLite database per shard with a single Go writer, and their backup pipeline snapshots the full DB file to S3 every few minutes—corruption was first detected when a downstream data pipeline reading those S3 backups reported an error.

Why: If you run SQLite in production and take file-level backups or snapshots (especially with WAL mode), you should run PRAGMA integrity_check against your backups routinely—Tailscale's corruption was invisible to the live writer and only surfaced from the backup consumer. Anyone shipping SQLite-backed services should review whether their backup method correctly handles WAL state.