Online Multiplayer and Game Backend
Make authority, replicated state, session transitions, persistence, and degraded network behaviour explicit and testable.
Use When
- A game has remote players, lobbies, matchmaking, dedicated/listen servers, replicated actors/state, or backend-owned progression.
Do Not Use When
- The request is local multiplayer only.
- Anti-cheat, moderation, or infrastructure deployment is the main task; compose with their specialist skills.
Required Inputs
Engine/version, player/region/load envelope, topology, trust boundaries, tick/update budgets, gameplay state model, matchmaking rules, persistence ownership, privacy/security constraints, service objectives, cost limits, and version policy.
Workflow
- Choose topology from threat, fairness, latency, cost, and operational evidence; name the authority for every mutable field.
- Specify session states from discovery through allocation, join, play, disconnect, reconnect, migration/termination, and cleanup.
- Define replicated state, relevance/frequency, RPC direction/reliability/idempotency, prediction/reconciliation, and late-join snapshots.
- Separate ephemeral match state from durable profile/economy state; make retries and ownership transfers safe.
- Version protocol and content contracts; test compatible skew and reject incompatible clients with a recoverable message.
- Exercise latency, loss, jitter, reorder, duplication, disconnect, reconnect, server crash, region loss, overload, and malicious input.
Quality Standards
- The server validates consequential actions; a client request is never proof that an action was legal.
- Reliable delivery is used only for state that must arrive; queues must be bounded.
- Tests retain seed, build/protocol version, topology, network profile, server logs, and outcome.
Anti-Patterns
- Client-authoritative competitive state. Fix: validate commands and outcomes at trusted authority.
- Happy-path local-network testing. Fix: exercise latency, jitter, loss, duplication, and partitions.
- Protocol break in one deployment. Fix: use versioned expand-contract compatibility windows.
- Reconnect creates duplicate effects. Fix: persist identity, sequence, idempotency, and resume state.
- Capacity inferred from averages. Fix: test peak concurrency, regional failure, queues, and recovery.
Outputs
Authority matrix; protocol/session contracts; replication budget; backend data ownership map; network test pack; capacity/region plan; compatibility and rollback runbook.
References
Evidence Produced
| Category | Artifact | Format | Example |
|---|---|---|---|
| Correctness | Multiplayer authority and network-condition test pack | Markdown plus test output | protocol, ownership, latency/loss, reconnect, duplicate action, cheat case, and recovery |


