Architecture overview – order platform

Current production topology · last verified 21 July 2026 · owner: platform team · green marks the checkout hot path

Components

Component	Responsibility	Notes
API gateway	Auth, rate limiting, routing	Stateless; scales horizontally
Order service	Checkout, order lifecycle	The hot path – p99 budget 250 ms
Catalog service	Product reads	95% cache hit rate; safe to degrade
Postgres	System of record for orders	Single writer; 7-day PITR window
Event queue	Order events fan-out	At-least-once; consumers are idempotent
Workers	Billing, notifications	Retry with backoff; dead-letter after 5

Decisions worth knowing

• Catalog degrades before checkout does – load-shedding drops browse traffic first.
• Billing is queue-consumer only: nothing on the checkout path waits on it.
• Dashed edge = catalog cache warms from order events, eventual by design.