feat: backend service

gateway/internal/session/session.go

@@ -13,27 +13,16 @@ var (
 	ErrNotFound = errors.New("session cache record not found")
 )
 
-// Cache resolves authenticated device-session state from the gateway hot-path
-// cache.
+// Cache resolves authenticated device-session state from the gateway
+// hot path. The implementation dropped the previous Redis projection: the only
+// implementation is *BackendCache, which calls backend's
+// `/api/v1/internal/sessions/{id}` synchronously per request.
 type Cache interface {
 	// Lookup returns the cached record for deviceSessionID. Implementations must
 	// wrap ErrNotFound when the cache does not contain the requested record.
 	Lookup(ctx context.Context, deviceSessionID string) (Record, error)
 }
 
-// SnapshotStore stores mutable session record snapshots inside one gateway
-// process and exposes the same read contract as Cache for the hot path.
-type SnapshotStore interface {
-	Cache
-
-	// Upsert stores record under record.DeviceSessionID, replacing any previous
-	// snapshot for that session.
-	Upsert(record Record) error
-
-	// Delete removes the local snapshot for deviceSessionID when it exists.
-	Delete(deviceSessionID string)
-}
-
 // Status identifies the cached lifecycle state of a device session.
 type Status string