system-design – Page 19 – Türker Yıldırım

The dotnet service that finally moved behind the same gateway

Deep diveApril 27, 202110 min read

One service in a different language, with its own auth, its own log format and its own deploy. The language was the least interesting difference.

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.

Fault injection: timeout, 500, and a slow trickle

NoteApril 21, 20211 min read

Every test mocks a fast success, and every production incident is one of the four failure modes nobody wrote a test for. The slow trickle is the one…

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 dead letter queue with nobody reading it is a bin

NoteApril 15, 20212 min read

Moving failed messages out of the main flow keeps the system healthy and does nothing on its own about the messages. The replay path is the part that…

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.

Priority is a separate queue, not a field

NoteMarch 31, 20212 min read

A priority field does not help when the worker is already four minutes into a nightly export. Splitting by latency requirement rather than by importance is the framing…

State locking, and the two applies that raced

NoteMarch 31, 20212 min read

Two applies against one state file at the same time produce a state that describes neither result, and the backend lock is the only thing that prevents it.…

A read model that is allowed to be wrong for four seconds

Deep diveMarch 17, 202114 min read

A report query with eleven joins, run on every dashboard load. One model cannot be shaped for both writing and reading past a certain size.

A circuit breaker without a half-open state never recovers

NoteMarch 9, 20212 min read

A breaker that opens on failure and closes on a timer either flaps or stays open, and the half-open state is what makes the recovery decision evidence-based. The…