profiling – Page 3 – Türker Yıldırım

EXPLAIN ANALYZE, and an estimate that was out by 40x

NoteApril 11, 20231 min read

The optimiser chose a plan based on an estimate of 200 rows where the real answer was 8,000, and only the actual execution shows the difference. The gap…

A read replica, and the six queries that could not use it

Deep diveMarch 16, 202314 min read

A primary at 80% CPU and reports running during the working day. Setting up the replica takes an afternoon; the consistency model takes a month.

The Dockerfile that finally stopped installing the world

Deep diveJanuary 25, 20238 min read

A 1.4 GB image and a six-minute build, for an application that is 40 MB of PHP. Most of it is build tooling that shipped by accident.

Error cause, and the stack you stopped losing

NoteDecember 29, 20222 min read

Wrapping an error in a more meaningful one used to discard the original, or required a non-standard property that nothing displayed. The tracker support lagging is the practical…

A cache invalidation bug that only appeared under load

Deep diveOctober 17, 202210 min read

Correct in every test, wrong for about one request in four thousand. A read that races a write, and a cache that keeps the loser.

The database that was 80% dead rows

Deep diveOctober 4, 202210 min read

180 GB on disk and 41 GB of data. A table that was deleted from daily and never shrank.

Web fonts that stopped blocking the render

Deep diveSeptember 28, 202210 min read

600ms of the largest contentful paint was a font file. font-display: block, and a page that renders in stages.

OpenTelemetry when the PHP SDK is still beta

Deep diveSeptember 20, 202210 min read

The traces specification is 1.0 and the PHP implementation is not. Three tracing formats and a vendor decision nobody wants to make.

A read-through cache that stampedes exactly once

Deep diveAugust 24, 202210 min read

A cache entry expired at 09:00 and four hundred requests recomputed it. A latency spike every hour, exactly on the hour.

An SLO that survived contact with the business

Deep diveMay 17, 202214 min read

99.9% was written in a document in 2020 and had never been measured. Three teams with three definitions of “up”.