Game Servers at Scale · Reference
Glossary
The vocabulary this course uses for shared-world servers, and the words it deliberately avoids.
The language of this course. A term is promoted here once a lesson has actually used it and you have used it back correctly — so this page grows more slowly than the lessons do. Where the wider field uses several words for one thing, this page picks one and lists the rest as aliases to avoid.
The loop
Tick: One iteration of the server’s simulation loop: drain the inputs that arrived, advance the world, send out what changed. Avoid: Frame, step, update cycle
Tick rate: How many ticks the server runs per second. The single number that multiplies almost every cost in the system — bandwidth, CPU, and latency floor all scale with it. Avoid: Server FPS, refresh rate
World state: The authoritative data describing everything in the game, held in the memory of the process that owns it. Not what is in the database, and not what a client currently believes. Avoid: Game state, the model, the data
Authoritative server: A server whose copy of the world state is the only one that counts. Clients send inputs and receive results; they never decide an outcome. Avoid: Master server, host, source of truth
Talking to clients
Input: A message from a client describing what a player wants to do — “move here”, “chop tree 42”. A request, not an instruction. The server is free to ignore it. Avoid: Command, action, event, packet
Snapshot: A message containing the complete world state a client is entitled to see, sent whole. The simplest thing that works, and the first thing to stop working. Avoid: Full sync, state dump
Broadcast: Sending the same outbound message to many clients in one tick. In this course, always ask what the recipient count is multiplied by — broadcast cost is never one number. Avoid: Fan-out, publish
Egress: Bytes leaving the server per second. The number that runs out first in a shared-world game, long before CPU does. Avoid: Upload, outbound traffic, throughput
Candidates
Introduced but not yet earned. These move up once a lesson has used them properly.
- Area of interest — the subset of the world one player is entitled to receive.
- Chunk — a fixed region of an endless world, used as the unit of interest and of ownership.
- Delta — a message describing only what changed since the last one.
- Backpressure — what a server does about a client that cannot receive as fast as the server can send.
- Entity interpolation — the client’s trick of drawing the recent past smoothly instead of the present jerkily.