Make the Reyden cache presence-based, dropping the dead tri-state

markReyden was the only writer and only ever stored isReyden: true, so the
CacheEntry.isReyden field and isKnownReyden's boolean | undefined return type
carried an unreachable "known not Reyden" state. Drop the field and return a
plain boolean: an unexpired entry means Reyden, its absence means not known.
Callers already used the result in a boolean context. Update the tests that
asserted the old undefined return to expect false.

Co-authored-by: Isaac <no-reply@databricks.com>
Signed-off-by: Rahul Singhal <rahul.singhal@databricks.com>

Author: rahuls-db

lib/ReydenWarehouseCache.ts

@@ -18,7 +18,6 @@ const TTL_MS = 6 * 60 * 60 * 1000; // 6 hours
 
 interface CacheEntry {
   timestamp: number;
-  isReyden: boolean;
 }
 
 class ReydenWarehouseCache {
@@ -54,23 +53,27 @@ class ReydenWarehouseCache {
 
   /**
    * Checks if a warehouse is known to be Reyden (requiring SEA fallback).
-   * Returns undefined if the warehouse is not in the cache or the entry has expired.
+   *
+   * Membership is presence-based: the cache only ever records known-Reyden
+   * warehouses (via markReyden), so an unexpired entry means Reyden and the
+   * absence of one means "not known" — there is no negative-cache state.
+   * Returns false when the warehouse is not in the cache or the entry expired.
    */
-  public isKnownReyden(host: string, warehouseId: string): boolean | undefined {
+  public isKnownReyden(host: string, warehouseId: string): boolean {
     const key = this.getKey(host, warehouseId);
     const entry = this.cache.get(key);
 
     if (!entry) {
-      return undefined;
+      return false;
     }
 
     // Opportunistically evict expired entries on access
     if (this.isExpired(entry)) {
       this.cache.delete(key);
-      return undefined;
+      return false;
     }
 
-    return entry.isReyden;
+    return true;
   }
 
   /**
@@ -91,10 +94,7 @@ class ReydenWarehouseCache {
       }
     }
 
-    this.cache.set(this.getKey(host, warehouseId), {
-      timestamp: now,
-      isReyden: true,
-    });
+    this.cache.set(this.getKey(host, warehouseId), { timestamp: now });
   }
 
   /**

tests/unit/thrift-backend/ReydenThriftRecovery.test.ts

@@ -46,7 +46,7 @@ describe('Reyden Warehouse Cache', () => {
       const host = 'example.com';
       const warehouseId = 'warehouse-123';
 
-      expect(reydenCache.isKnownReyden(host, warehouseId)).to.be.undefined;
+      expect(reydenCache.isKnownReyden(host, warehouseId)).to.be.false;
       reydenCache.markReyden(host, warehouseId);
       expect(reydenCache.isKnownReyden(host, warehouseId)).to.be.true;
     });
@@ -66,7 +66,7 @@ describe('Reyden Warehouse Cache', () => {
       reydenCache.markReyden(host, 'warehouse-1');
 
       expect(reydenCache.isKnownReyden(host, 'warehouse-1')).to.be.true;
-      expect(reydenCache.isKnownReyden(host, 'warehouse-2')).to.be.undefined;
+      expect(reydenCache.isKnownReyden(host, 'warehouse-2')).to.be.false;
     });
 
     it('should isolate entries by host', () => {
@@ -75,7 +75,7 @@ describe('Reyden Warehouse Cache', () => {
       reydenCache.markReyden('host1.com', warehouseId);
 
       expect(reydenCache.isKnownReyden('host1.com', warehouseId)).to.be.true;
-      expect(reydenCache.isKnownReyden('host2.com', warehouseId)).to.be.undefined;
+      expect(reydenCache.isKnownReyden('host2.com', warehouseId)).to.be.false;
     });
 
     it('should have cache size method', () => {
@@ -95,7 +95,7 @@ describe('Reyden Warehouse Cache', () => {
 
       reydenCache.clear();
       expect(reydenCache.size()).to.equal(0);
-      expect(reydenCache.isKnownReyden('host1.com', 'warehouse-1')).to.be.undefined;
+      expect(reydenCache.isKnownReyden('host1.com', 'warehouse-1')).to.be.false;
     });
   });
 
@@ -124,7 +124,7 @@ describe('Reyden Warehouse Cache', () => {
 
       // One tick past the TTL: expired, evicted on access.
       clock.tick(1);
-      expect(reydenCache.isKnownReyden(host, warehouseId)).to.be.undefined;
+      expect(reydenCache.isKnownReyden(host, warehouseId)).to.be.false;
       expect(reydenCache.size()).to.equal(0);
     });
 

tests/unit/thrift-backend/ReydenThriftRecoveryOrchestration.test.ts

@@ -104,7 +104,7 @@ describe('Reyden Thrift Auto-Recovery — Orchestration', () => {
 
     expect(thrown).to.equal(genericError);
     expect(kernelStub.called).to.be.false; // No kernel fallback for a non-Reyden error.
-    expect(reydenCache.isKnownReyden(HOST, WAREHOUSE_ID)).to.be.undefined; // Not marked.
+    expect(reydenCache.isKnownReyden(HOST, WAREHOUSE_ID)).to.be.false; // Not marked.
   });
 
   it('preserves the Thrift rejection as cause when the kernel fallback also fails', async () => {