cascadingCache()

Creates a singleton reactive cache with N-tier cascading lookup.

Each cached entry is a state() store. On cache miss, tiers are tried in order (index 0 = hottest/fastest). When a lower tier hits, the value is auto-promoted to all faster tiers. Concurrent lookups for the same key share the same state instance — natural dedup without keyedAsync.

Note: undefined is used as the "not yet loaded" sentinel. Tiers that return undefined are treated as cache misses. Do not store undefined as a meaningful value.

Signature

function cascadingCache<V>(
	tiers: CacheTier<V>[],
	opts?: CascadingCacheOptions,
): CascadingCache<V>

Parameters

Parameter	Type	Description
tiers	CacheTier<V>[]	Ordered lookup tiers, hottest first.
opts	CascadingCacheOptions	Optional configuration (maxSize, eviction policy, writeThrough).

Returns

CascadingCache<V> — a reactive cache where each entry is a WritableStore<V | undefined>.

Basic Usage

import { cascadingCache } from 'callbag-recharge/utils';
import { subscribe } from 'callbag-recharge/extra';

const cache = cascadingCache([
    { load: k => memoryMap.get(k), save: (k, v) => memoryMap.set(k, v) },
    { load: k => fetch(`/api/${k}`).then(r => r.json()) },
  ]);

const user = cache.load("user:42"); // WritableStore<User | undefined>
subscribe(user, v => console.log("user:", v));
user.get(); // value or undefined (if async tier pending)