export type ActiveIndexVersion = {
    physical_name: string;
    provider: string;
    version: number;
};
/**
 * Caches which physical index currently serves reads for every logical index,
 * since that can change out from under a running process when another
 * replica finishes seeding and flips it.
 *
 * Populated in one bulk fetch rather than one per index: there are never many
 * search indexes in an app, so listing them all is cheap, and it means
 * refreshing because of one index refreshes every other one for free.
 *
 * Fresh for `SOFT_TTL_MS`. Stale beyond that but still served while a
 * background refresh runs (stale-while-revalidate) — a failed refresh leaves
 * `fetchedAt_` untouched, so the age keeps counting from the last *successful*
 * fetch rather than resetting. Never served past `HARD_TTL_MS` since that last
 * success; a caller waits on a synchronous refetch instead.
 */
export declare class ActiveIndexVersionCache {
    protected readonly fetchAll_: () => Promise<Map<string, ActiveIndexVersion>>;
    protected values_: Map<string, ActiveIndexVersion>;
    protected fetchedAt_: number;
    protected refreshing_?: Promise<void>;
    constructor(fetchAll_: () => Promise<Map<string, ActiveIndexVersion>>);
    get(name: string): Promise<ActiveIndexVersion>;
    protected refresh(): Promise<void>;
    /** Sets one value directly, e.g. right after this process itself flips it. */
    set(name: string, value: ActiveIndexVersion): void;
    invalidate(): void;
}
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