merged from gramsrv upstream

internal/store/active_channel_ids_cache.go

@@ -0,0 +1,28 @@
+package store
+
+import "context"
+
+// ActiveChannelIDsPageKey identifies one immutable page of the durable
+// owner-scoped active membership read model. Generation is the exact
+// channel_active_memberships hash, or the documented missing-generation
+// sentinel used before an owner has any membership row.
+type ActiveChannelIDsPageKey struct {
+	UserID         int64
+	Generation     int64
+	AfterChannelID int64
+	Limit          int
+}
+
+// ActiveChannelIDsPageCache is a rebuildable shared L2. Redis errors are
+// returned so callers cannot silently turn an outage into a PostgreSQL
+// stampede.
+type ActiveChannelIDsPageCache interface {
+	GetActiveChannelIDsPage(context.Context, ActiveChannelIDsPageKey) ([]int64, bool, error)
+	PutActiveChannelIDsPage(context.Context, ActiveChannelIDsPageKey, []int64) error
+}
+
+// ActiveChannelIDsPageLoader is the bounded authoritative cold source used
+// only after a shared-cache miss.
+type ActiveChannelIDsPageLoader interface {
+	ListActiveChannelIDsForUser(context.Context, int64, int64, int) ([]int64, error)
+}