Mastering FastAPI Background Tasks: Real‑World Patterns, Testing, and When to Reach for Celery

Short summary

A deep dive into FastAPI's BackgroundTasks class for lightweight fire-and-forget jobs, covering request lifecycle, execution context, and error handling. Includes practical patterns for async email sending and CSV ingestion, plus guidance on when to switch to Celery or RQ for long-running or retry-dependent work. Code examples and testing strategies are provided throughout.

• •BackgroundTasks runs in the same event loop — use async or threadpool for I/O
• •Best for sub-second jobs; use Celery/RQ for retries, durability, or multi-minute tasks
• •Includes patterns for email sending, CSV ingestion, and resource-leak avoidance

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