Glossary
Every term the courses use, defined in one line and then in a paragraph. Written to be read out of order.
Showing 15 of 124
Work that runs because of the time, not a user.
A job triggered on a schedule. Fails in four classic ways: timezones, overlapping runs, missed runs, and growing workloads. Alert on the absence of success, not on failure.
See also Cron, Background job, UTC
The declared shape of your data.
Which tables exist, which columns they have, and what is allowed in them. Changing it is a migration. In schemaless databases the schema still exists, just in your code instead of the database.
The part of a URL after the question mark.
Key-value pairs carrying page state: filters, queries, sorting. Putting state here makes it shareable, survivable across refreshes, and correct with the back button. Validating it means a hand-edited URL degrades instead of crashing.
See also State, Validation
Any value that grants access.
A database password, an API key, a signing key. Never in code, never in a client bundle. If one leaks, revoke it first. Deleting the line comes second, and git history keeps it regardless.
See also Environment variable, Key rotation
A program that is open for business.
A running program listening for requests and answering them. Not a piece of hardware: one machine can run several, and it stops being a server the moment the program exits. Your laptop runs one every time you start a dev command.
A function you call from the client that runs on the server.
Written like a normal function, but the build replaces the body with a network call in the client bundle and the real implementation only ever exists on the server. You get a typed contract for free and the server code never ships to the browser.
See also RPC, Validation, Secret
Data fetched from an API, held in the UI.
Not really your application’s state, but a cache of somebody else’s, which goes stale the moment anyone else changes it. Treating it as local state is what produces "I updated it but the list still shows the old value".
You ship a function; something else runs it.
The platform decides when to run your code, how many copies to run, and when to discard them. Costs nothing while idle, scales without thought, and gives you no persistent memory between requests.
See also Cold start, Stateless, Container
The server-side record that you are logged in.
A stored record the server looks up on each request using an id from a cookie. Slower than a signed token because of the lookup, but logging out is instant and reliable.
See also Cookie, JWT, Authentication
A grey outline shown while content loads.
A placeholder in the shape of the coming content. Tells the user what to expect and prevents the page jumping when data arrives, which a spinner does neither of.
See also Loading state, Empty state
The language for asking relational databases questions.
The query language of relational databases. Also used loosely to mean the relational family itself (Postgres, MySQL, SQLite) as opposed to NoSQL.
Data that can change.
The real question is never what the state is but where the authoritative copy lives: the server, the URL, component memory, or browser storage. Two copies of the same fact will eventually disagree.
See also Server state, Search params
Each request starts from nothing.
The server remembers nothing about you between requests by default. Memory has to be added deliberately, which is exactly what cookies and sessions are for.
See also HTTP, Session, Serverless
A three-digit verdict on a request.
The first digit is what matters: 2xx worked, 3xx moved, 4xx you asked wrong, 5xx they broke. The 4 versus 5 distinction decides whether retrying can possibly help.
See also HTTP, Retry, Rate limit
Sending a response in pieces as it is produced.
Delivering output progressively instead of waiting for all of it. Does not make anything faster; makes waiting tolerable, which is usually the real problem. Applies to slow page data as much as to model output.