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docs/MIGRATION-INMEMORY.md

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+# Migration to the in-memory engine
+
+This release removes the external coordination backend entirely.
+
+## Removed configuration
+
+Delete these old top-level/settings from existing configuration files:
+
+```text
+redis
+scheduler.distributed
+scheduler.lease_ttl
+scheduler.poll_interval
+workers[].request_lease_ttl
+usage.redis_aggregates
+cluster
+```
+
+Replace the old local/cluster visualization settings with:
+
+```json
+"infrastructure": {
+  "node_name": "mac-studio-gateway",
+  "refresh_interval": "250ms",
+  "max_requests": 256
+}
+```
+
+The configuration parser uses `DisallowUnknownFields`, so obsolete settings fail fast instead of being silently ignored.
+
+## Runtime behavior
+
+The following state now exists only inside one gateway process:
+
+- weighted fair queue state;
+- running concurrency;
+- per-worker slots;
+- actor and tenant quota buckets;
+- runtime policy overrides;
+- browser sessions;
+- usage summaries;
+- live/infrastructure telemetry.
+
+Active scheduling state still resets on restart. Durable control-plane state (UI-created API-key hashes, policy overrides, quota balances, metrics snapshots and usage history) is now stored locally under `storage.data_dir`; the inference scheduler itself remains in memory.
+
+## Multiple Ollama workers
+
+No change is required. One gateway may still route to many Ollama workers and maintains one fair queue across all of them.
+
+## Multiple gateway processes
+
+Do not place multiple independent gateway processes behind a generic load balancer if you require strict global fairness. Each process is now a separate fairness/quota/session domain.
+
+For the intended deployment, use one authoritative gateway and scale the Ollama worker pool behind it.
+
+## API change
+
+The former cluster visualization endpoints are now local infrastructure endpoints:
+
+```text
+GET /gateway/ui-api/infrastructure
+GET /gateway/ui-api/infrastructure/stream
+```
+
+The web UI has been updated accordingly.