profiling – Page 6 – Türker Yıldırım

Two hundred integration tests that share one database

Deep diveMay 27, 202110 min read

A suite that passes alone and fails in a different order. Test 141 depends on a row test 88 created, and nobody wrote that down.

An index that made writes slower than the reads it saved

Deep diveApril 23, 202110 min read

Eleven indexes on a table with a heavy write path. Every index is a write amplification that nobody measured, and three of them were never used.

Octane keeps the application in memory and finds every static you left

Deep diveApril 21, 202110 min read

40ms becomes 8ms, and the fourth request returns another customer’s data. The shared-nothing assumption is load-bearing in more places than anybody had counted.

A forced-trace header, behind a permission check

NoteApril 18, 20211 min read

Reproducing a problem with a header is far better than “try again while I watch the dashboard”, and it must not be a way for anybody to trace…

The staging environment that was lying

Deep diveApril 8, 202110 min read

It passed on staging four times and failed in production four times. The same code, a different outcome, and five differences nobody had enumerated.

useEffect with an empty array is not componentDidMount

NoteMarch 11, 20212 min read

An effect with an empty dependency array runs once after the first render, which resembles a mount hook and differs in when it fires and what it can…

Log lines that a machine can read

Deep diveMarch 4, 202110 min read

A grep that needed three regular expressions and a sort. A log line written for a person to read at leisure is not a record you can query.

The cache that returned stale data for eleven days

Deep diveMarch 4, 202110 min read

A price change that took eleven days to reach one page. Three caches, and only one of them was being cleared.

A laptop profile is a hypothesis, not a finding

NoteFebruary 25, 20211 min read

Four differences between a development machine and production can each invert the conclusion a profile suggests. The dataset difference is the one that inverts rather than scales: an…

A data provider runs before setUp

NoteFebruary 22, 20212 min read

Providers are collected during test discovery, long before any setUp has run, so a provider touching the application container or the database fails. String keys on the provider…