Background job
InfrastructureWork done after the response is sent.
Work moved out of the request so the user is not left waiting: sending email, processing an upload, generating a report. Requires somewhere to report progress and somewhere to report failure.
See also Queue, Worker, Cron
Hallucination
AI in the stackA confident, fluent, false answer.
Fabricated output produced by exactly the same process as correct output, which is why it looks equally convincing. Inherent to how models work rather than a bug to be patched. Fluency carries no information about accuracy.
See also RAG, Grounding
Idempotency
InfrastructureDoing it twice has the same effect as doing it once.
A property that makes retrying safe. Usually achieved with a key the caller sends on every attempt; the server records processed keys and returns the original result instead of repeating the work. This is what prevents double charges.
See also Retry, At-least-once, Endpoint
Latency
InfrastructureTime spent waiting rather than working.
The delay before a response begins. Largely set by physical distance and the number of round trips, not by processing speed. London to Virginia is about 80ms round trip no matter how good your code is.
See also Round trip, Edge, CDN
Process
InfrastructureA running program.
One instance of your code, executing. A server is a process that is listening; when it exits, the server is gone even though the machine is still on.
See also Server, Port
Worker
InfrastructureA process that pulls jobs off a queue and does them.
Separate from your web app, so you can deploy one without interrupting the other and add more workers to drain a backlog faster.
See also Queue, Background job