architecture – Page 34 – Türker Yıldırım

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.

Domain events are past tense, always

NoteMarch 3, 20212 min read

An event names something that has already happened and cannot be refused, which is the property that separates it from a command. The naming convention is not cosmetic…

Two services sharing a database are one service

NoteFebruary 24, 20212 min read

Independent deployment is the property that makes a service a service, and a shared schema removes it regardless of how the code is organised. The usual path to…

An OpenAPI document that is the test suite’s source of truth

Deep diveFebruary 23, 202110 min read

3.1 lands in February with real JSON Schema. Generating docs from code fixes half the problem; making the document the contract fixes the other half.

Glob imports, and the routes directory that registers itself

NoteFebruary 22, 20212 min read

A directory of route modules had an index file listing them, and the file was updated by hand every time somebody added one. The lazy form is what…

The N+1 that only appeared in the API serialiser

Deep diveFebruary 14, 202110 min read

A controller with eager loading and four hundred queries anyway, because the query count depends on which fields the client asked for.

A queue worker that stops cleanly

Deep diveFebruary 11, 202110 min read

A deploy killed a worker mid-job and a customer was charged without an order. SIGTERM, a grace period that was too short, and the job that must be…

At-least-once delivery means your handler is idempotent

NoteFebruary 2, 20212 min read

Exactly-once delivery is not available from any broker worth using, so the handler has to tolerate seeing the same message twice. The claim and the work must be…

A value object is not an entity and the difference is identity

NoteJanuary 14, 20212 min read

Two entities with identical fields are different things; two value objects with identical fields are the same value. The practical consequence is that value objects need no table,…