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Module · 5 lessons
Async, Background Work, and Streaming
Handle concurrency and long-running work: async/await for high throughput, background tasks for post-response jobs, streaming responses, SSE, and WebSockets.
At a glance
Level
Intermediate to Advanced
Lessons
5 lessons
Time to complete
1 week
Cost
Free forever · no sign-up
Welcome to Async, Background Work, and Streaming, the seventh module of the course. So far every endpoint has done one quick thing and returned. Real systems need more: to stay responsive while waiting on slow I/O, to kick off work that outlives the response, to send data as it’s produced instead of all at once, and sometimes to hold a live two-way connection. This module covers all four, and they’re some of the most useful — and impressive — things FastAPI can do.
You’ll start with async/await and concurrency: what async def actually buys you, when it helps (and when it doesn’t), and how FastAPI runs both styles. You’ll run jobs after the response with background tasks, stream responses chunk-by-chunk (including server-sent events for live updates), and open a WebSocket for real-time, bidirectional messaging. The module ends with a guided project: a streaming endpoint that sends a long response token-by-token — exactly the pattern behind streaming chat and AI responses.
Every example is real, runnable code verified end to end. Start with Lesson 1, where you’ll learn what async really means for your API.
Lessons in this module
1
async and Concurrency
Understand what async/await really does in FastAPI: how the event loop serves many requests during I/O waits, and when to reach for async def versus a plain def.
2
Background Tasks
Return a response instantly and run slower work afterward — emails, logging, cleanup — with FastAPI's BackgroundTasks, plus when to reach for a real task queue.
3
Streaming and Server-Sent Events
Send data as it's produced with StreamingResponse, and push live updates to clients with Server-Sent Events — perfect for logs, progress, and token-by-token output.
4
WebSockets
Open a persistent, two-way connection with WebSockets for real-time apps — accept a connection, exchange messages in a loop, and handle disconnects cleanly.
5
Guided Project: Streaming Endpoint
Build a token-by-token streaming endpoint — the pattern behind streaming chat and AI responses — with StreamingResponse and an async generator.
Achievement
Complete all 5 lessons to finish the Async, Background Work, and Streaming module.