Add load balancing

[vcarl]

Load Balancer Architecture

Track horizontal scaling implementation using deterministic guild sharding.

Architecture

Load Balancer → HTTP Service (stateless, 2-10 pods)
                    ↓
              hash(guildId) % NUM_PODS → Gateway Pod N
                    ↓
              SQLite + Litestream → DO Spaces

Issues

Issue	Title	Tier	Risk	Status
#229	Litestream backup sidecar	1	Low	Open
#230	Ingress rate limiting/timeouts	1	Very Low	Open
#231	PostgreSQL StatefulSet	-	-	Closed
#232	SERVICE_MODE support	3	Medium	Open
#233	Config service	-	-	Closed
#234	HTTP service + deterministic routing	3	Medium	Open
#235	Gateway StatefulSet + shard filtering	4	High	Open

Dependencies

#229 (Litestream) ──┐
                    ├── #232 (SERVICE_MODE) ── #234 (HTTP) ──┐
                    │                                        ├── #235 (Gateway)
                    └────────────────────────────────────────┘

Key Decision: Deterministic Sharding

Eliminated config service (#233) and PostgreSQL (#231) in favor of deterministic sharding:

const podOrdinal = hash(guildId) % NUM_GATEWAY_PODS;
const gatewayUrl = `http://gateway-${podOrdinal}.gateway-internal:3000`;

Benefits: Simpler, no external state, no network lookups
Trade-off: Scaling requires coordination (all pods recalculate)

References

• PR Architecture analysis: Load balancing with SQLite constraint #228: Architecture analysis
• /notes/LOAD_BALANCER_QUICK_REF.md