Glossary
Every term the courses use, defined in one line and then in a paragraph. Written to be read out of order.
Showing 13 of 124
A kept copy of something expensive to produce.
A stored result reused instead of being recomputed or refetched. The most effective performance tool available and the source of the most confusing bugs, because a copy can be out of date. Copies live in the browser, the CDN, and your server.
See also CDN, Invalidation, TTL
Copies of your files in many places worldwide.
A content delivery network keeps copies of static files at locations around the world so users are served from somewhere near them. Cheap, effective, and a place stale content loves to hide.
Automation that tests and ships your changes.
Continuous integration runs checks on every change; continuous delivery deploys the ones that pass. The value is that the deploy path is exercised constantly rather than only on the day it matters.
See also Build, Deploy, Preview deployment
The side making the request, usually a browser.
Whatever asks for something: a browser, a mobile app, another server. Crucially it runs on a machine the user controls, so nothing it claims can be trusted without verification.
See also Server, Validation
The delay when no instance is running yet.
When a serverless function has no live instance, one must be created before your code runs. That startup delay is the price of paying nothing while idle, and it lands on whichever unlucky visitor arrives first.
See also Serverless, Stateless
More than one thing happening at the same time.
Simultaneous operations touching the same data. Almost everything a database offers exists to make concurrency safe. Without it, a plain file would be fine.
See also Transaction, Integrity
The user agreeing to share something.
The step in a sign-in flow where the user approves what your app is allowed to see. Their agreement, not yours, and revocable by them at any time.
See also OAuth, Identity provider
An app packaged with everything it needs to run.
Your application plus its exact dependencies and configuration, sealed into one unit that runs identically anywhere. Largely kills "works on my machine" by removing the differences between machines.
See also Serverless, Environment
How much a model can consider at once.
The total amount of text (input and output together) a model can have in front of it for a single call. A hard limit. When a conversation exceeds it, earlier messages must be dropped or summarised.
See also Token (model), Prompt caching
The agreed shape of messages between systems.
What each side promises the other about requests and responses. Exists whether or not anyone wrote it down. Shared types turn a broken contract into a build error instead of a production incident.
See also API, Breaking change
A small value the browser attaches to every request.
How a stateless protocol manages to remember you. The browser stores it and sends it automatically with each request to that site. Marking one HttpOnly prevents JavaScript from reading it, which stops an injected script stealing a session.
Work triggered by the clock.
A scheduled job: nightly cleanup, hourly reindex, the weekly digest. Named after a Unix utility from the 1970s. Fails silently by default, because nobody is waiting for it.
See also Scheduled job, Background job, UTC
How a page looks.
Describes presentation: colour, size, spacing, layout. Separate from structure on purpose: remove it and the page is ugly but still works and still makes sense.