Configurable Channel and Zone cache strategies

[rafabernad]

Proposal

Expose two configurable cache extension points:

• ChannelCacheStrategy for storing, resolving and invalidating individual Channels;
• ZoneCacheStrategy for loading, storing and invalidating the Zone list.

The default implementations use a short-lived process-local L1 and the globally configured CacheStrategy as a longer-lived L2. Channel entries are keyed by token, include a dedicated default-Channel key and coalesce concurrent misses. Zone operations receive the RequestContext and a loader callback.

Channel and Zone mutations update or invalidate both cache levels. Custom implementations can control cache behavior without changing ChannelService or ZoneService.

CacheStrategy lifecycle

CacheService owns initialization and destruction of the global CacheStrategy. Lazy single-flight initialization ensures that early cache access and the Nest lifecycle share one initialization attempt. Failed initialization can be retried, and teardown runs only after successful initialization.

Compatibility

Both strategy properties are optional and have default implementations. No database schema or GraphQL API changes are required.

Performance

A compiled-code microbenchmark measured a hot L1 lookup at approximately 0.4 µs. With very small Channel counts, this adds approximately 0.1–0.2 µs relative to an array lookup; from roughly 100 cached Channels onward, the O(1) lookup is faster. An L2 hit using the in-memory CacheStrategy, including deserialization and entity rehydration, measured approximately 4.2 µs.

Pull request

• feat(core): add configurable Channel and Zone cache strategies #5248

Related work

• Cache strategy for channels in ChannelService #988
• Introduce a CacheStrategy for multi-instance data caching #3043
• ChannelService.findAll cache uses the API query limit #2233

[rafabernad]

A proposed implementation is now available in #5248.