Architecture

Software architecture patterns and system design notes: how to structure code within a service, and how services communicate with each other.

Articles

• DDD & the Service Layer — structuring FastAPI projects by domain, and keeping business logic in a service layer instead of the router.
• Event-Driven Architecture: Kafka vs. SQS vs. RabbitMQ — event-driven basics and how the three major messaging systems compare.
• Kafka Consumers Behind a FastAPI API on Kubernetes — consumer groups, background tasks vs. blocking startup, pod-local state, and when to split the consumer into its own deployment.
• Dependency Inversion via Interfaces and Abstract Classes — the SOLID principle behind DI, and abc.ABC as the nominal-typing way to express the abstraction it requires.
• Understanding Consistency in Distributed Systems — strong vs. eventual consistency, why replication introduces staleness, and a checklist for choosing the right guarantee per piece of data.
• Senior Software Engineer Architecture Interview Cheat Sheet — a problem-to-pattern table for recurring architecture and distributed-systems interview questions, plus a response template.

Patterns

Code-level design patterns — how you structure and construct objects within a service — live in their own Patterns subsection, separate from the broader architectural styles above. Dependency Injection and the Factory Pattern below are both concrete, code-level ways of achieving the Dependency Inversion principle described above them:

• Dependency Injection with Protocols — structural typing with typing.Protocol instead of ABC inheritance, and why that avoids hierarchy hell.
• Factory Pattern in Python — from a plain function to registries to @classmethod alternative constructors.

Contributing

Learned a new architecture pattern or design principle worth keeping? Add it here as its own file. See Contributing for the how-to.