import { KV2 } from "./cached-kv.js";
import { UpstreamKV } from "./upstream-kv.js";
import type { BlobStore, CacheLike, Tracer } from "./types.js";
export interface UpstreamConfig {
    /**
     * Environment to fall back to.
     * @default same as current VERCEL_ENV
     */
    env?: string;
    /**
     * Branch to fall back to.
     * @default 'main'
     */
    branch?: string;
}
export interface CreateKVOptions {
    /**
     * User-defined prefix within the env/branch namespace.
     * Example: "users/" -> cached-kv/production/main/users/{key}.value
     */
    prefix?: string;
    /**
     * Override the environment. Defaults to VERCEL_ENV.
     * Useful for local development or testing.
     */
    env?: string;
    /**
     * Override the branch. Defaults to VERCEL_GIT_COMMIT_REF.
     * Useful for local development or testing.
     */
    branch?: string;
    /**
     * Upstream environment for CoW fallback reads.
     *
     * - undefined (default): falls back to same env + 'main' branch
     * - { env, branch }: custom upstream
     * - null: disable fallback (isolated environment)
     *
     * @default { env: VERCEL_ENV, branch: 'main' }
     */
    upstream?: UpstreamConfig | null;
    /**
     * Blob access token (defaults to BLOB_READ_WRITE_TOKEN).
     */
    token?: string;
    /**
     * Blob store implementation (defaults to VercelBlobStore).
     */
    blobStore?: BlobStore;
    /**
     * Cache implementation for testing (defaults to Vercel Runtime Cache).
     */
    cache?: CacheLike;
    /**
     * Cache TTL in seconds (default: 3600).
     */
    cacheTtl?: number;
    /**
     * Byte threshold for large value separation (default: 1MB).
     */
    largeValueThreshold?: number;
    /**
     * Tracer for performance monitoring (defaults to no-op).
     */
    tracer?: Tracer;
}
/**
 * Create a KV store with automatic environment detection and CoW fallback.
 *
 * - On production/main: returns KV2 directly (zero overhead)
 * - On preview branches: returns UpstreamKV with fallback to upstream
 *
 * @example
 * ```ts
 * // Auto-detect environment
 * const kv = createKV();
 *
 * // Preview -> production fallback
 * const kv = createKV({ upstream: { env: 'production' } });
 *
 * // Isolated (no fallback)
 * const kv = createKV({ upstream: null });
 * ```
 */
export declare function createKV<M = undefined>(options?: CreateKVOptions): KV2<M> | UpstreamKV<M>;
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