- FastAPI – Dependency Injection in Practice
The feature FastAPI is built on. Depends(), dependencies that yield so setup and teardown live together, sub-dependencies, and collapsing the whole thing into one readable Annotated alias so a route signature states its own security rules. Then dependency_overrides, which is what makes any of it testable — and the reason an override keyed on the wrong function object silently does nothing.
- FastAPI – Project Structure That Survives Growth
The question the official docs answer least well. How a single main.py becomes routes, services, repositories, schemas and models — what belongs in each layer, and the rules that keep them apart: routes own HTTP, services own the rules, and repositories never commit because only the caller knows where a transaction ends. Plus typed settings read once, so a misspelt variable is a startup error.
- AWS – CloudFormation: Infrastructure You Can Re-create
Click-ops is fine until the day you have to build it again. A template's five sections, parameters and outputs, change sets so you see what an update will do before it does it, and SAM as the shorthand that turns forty lines of Lambda plumbing into six. Then the trap that ships stale config in silence: CloudFormation keeps the previous value for any parameter an update omits — it does not read your new default.
- FastAPI – Pydantic Models and Validation
Pydantic v2 as FastAPI actually uses it. Field constraints, field and model validators, computed fields for values that change at midnight, and separating the model you store from the model you return. Includes the snake_case-to-camelCase boundary that lets Python and TypeScript each keep their own conventions, and a field named `property` that breaks the `property` builtin twenty lines later.
- FastAPI – Routes, Parameters and Status Codes
Everything that turns an HTTP request into typed Python arguments. Path and query parameters, constraints with Query(), why Annotated is the form to learn, header and cookie parameters, choosing a status code, and splitting an API across routers with APIRouter. Including the repeated query parameter that needs no parsing, and the alias that lets a Python snake_case argument read as camelCase on the wire.