4 lessons
Why not everything belongs in the request
The difference between work a user needs an answer to right now and work that can happen after the response is already sent.
Message queues and background workers
The mechanism that reliably runs deferred work outside the request, and why it also protects services from traffic spikes.
Scheduled jobs and cron
Work that isn't triggered by any request at all, but needs to run automatically on a timer, and how to do it safely across multiple servers.
Putting the async pieces together
How synchronous requests, queues, workers and scheduled jobs combine into real multi-step background pipelines.