Emit a message from the request, and let a CLI worker run the slow part. Redis, Predis, RabbitMQ, and Amazon SQS in version 6.x.
The web request emits a message and answers right away. A worker does the slow part.
Signup, password reset, or order mails go out from the worker. The request returns before the SMTP server even answers.
Render the PDF, store it, and attach it to an email in the background. The user clicks once and moves on.
Resize uploads, cut thumbnails, or start a transcode. Heavy CPU work stays off the web servers.
Recalculate stats, aggregate reports, or clean up records in small messages that several workers share.
Parse a large CSV or build an export file row by row. Tell the user when it is ready instead of making them wait.
Deliver outgoing webhooks from a worker. RetryTrait tries again with a growing delay when the receiver is down.
Sync orders to an ERP, push contacts to a CRM, or call a slow payment API without holding a PHP-FPM process.
Fan out push, SMS, or in-app notifications to many users from one emitted message.
Update Elasticsearch, Meilisearch, or a search table after a save, so the write itself stays fast.
Rebuild expensive cache entries after a deploy or a content change, before the next visitor asks for them.
Send a reminder in 24 hours or expire a reservation in 15 minutes with executeAt on Redis or Predis.
If it does not have to finish before the response, emit a message and let a handler do it.
A user registers. The web app emits a user.registered message and answers in milliseconds. The worker, a separate CLI process started with php bin/worker.php, takes the message and sends the welcome email. When SMTP times out, RetryTrait sends a copy and the next attempt succeeds.
Redis via ext-redis, Predis, lazy RabbitMQ, and Amazon SQS. Each one implements DriverInterface.
RetryTrait schedules another attempt when a handler throws. The delay is real on Redis and Predis.
Redis drivers keep a separate set per priority and always poll the highest priority first.
Stop a worker from a shared file or a Redis key. The process manager is what starts it again.
A driver is send, wait, and setupPriorityQueue. A handler is one handle method.
Run the same CLI script on several processes. Redis SPOP and the brokers hand each message to one of them.
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