A reference ETS adapter for the optional completed-response cache.

Bounded and TTL-aware. :ets has no native TTL, so each entry carries an expiry monotonic-time deadline and get/1 rejects expired entries (and lazily deletes them). A max-entries cap bounds steady-state memory; when the cap is reached put/3 evicts the single oldest-by-deadline entry before inserting, which keeps the hot set resident under churn without a background sweeper.

The adapter is NOT admission authority — AshOnetime validates every field of a returned entry against the authoritative PostgreSQL claim before using the payload (see AshOnetime.Cache). Treat every entry as untrusted.

Supervision

The ETS table is owned by a GenServer started via start_link/1. Add it to your supervision tree (it owns the table; if it terminates the table is destroyed, which is safe — the cache is optional and a miss falls through to PostgreSQL):

children = [
  # ...your repo...
  {AshOnetime.Cache.Ets, max_entries: 10_000}
]

Then configure it as the cache module:

config :ash_onetime, cache: AshOnetime.Cache.Ets

The table is named __MODULE__ (one ETS cache per VM). A multi-instance deployment (e.g. one cache per tenant prefix) wraps this module behind a per-instance module so each gets its own __MODULE__-named table; the reference adapter is single-instance by design.

Options

• :max_entries — the bounded cap; put/3 evicts the oldest-by-deadline entry when the cap is reached before inserting (default 10_000). The cap bounds entry COUNT only — the per-entry byte ceiling is enforced upstream by AshOnetime.Cache (max_entry_bytes).

Limitations

This is a reference adapter tuned for simplicity and correctness, not throughput: the eviction is a single oldest-by-deadline scan, and expired entries are reaped lazily on get/1 rather than by a background sweeper. A high-throughput deployment should reach for Redis or a dedicated cache with sampled-LRU eviction and active expiry; this adapter exists so the cache-degradation path in AshOnetime.Cache is reachable without a third-party dependency.