---
title: Caching
description: Add a caching layer to your self-hosted c15t backend for production performance.
---
The backend includes a caching layer for frequently accessed data like GVL (Global Vendor List) lookups and custom server-side translations. By default, an in-memory cache is used — suitable for single-instance deployments. For production with multiple instances, plug in Redis or Cloudflare KV so all instances share the same cache.

## In-Memory (Default)

No configuration needed. The default memory cache has a 5-minute TTL and is suitable for development and single-instance deployments.

## Upstash Redis

```ts title="c15t.ts"
import { c15tInstance } from '@c15t/backend';
import { createUpstashRedisAdapter } from '@c15t/backend/cache';

export const c15t = c15tInstance({
  // ...
  cache: {
    adapter: createUpstashRedisAdapter({
      url: process.env.UPSTASH_REDIS_REST_URL,
      token: process.env.UPSTASH_REDIS_REST_TOKEN,
    }),
  },
});
```

If you already have an Upstash Redis client, pass it directly:

```ts
import { createUpstashRedisAdapterFromClient } from '@c15t/backend/cache';
import { Redis } from '@upstash/redis';

const redis = new Redis({
  url: process.env.UPSTASH_REDIS_REST_URL,
  token: process.env.UPSTASH_REDIS_REST_TOKEN,
});

const adapter = createUpstashRedisAdapterFromClient(redis);
```

## Cloudflare KV

For Cloudflare Workers deployments:

```ts title="worker.ts"
import { c15tInstance } from '@c15t/backend';
import { createCloudflareKVAdapter } from '@c15t/backend/cache';

export default {
  async fetch(request: Request, env: Env) {
    const c15t = c15tInstance({
      // ...
      cache: {
        adapter: createCloudflareKVAdapter(env.GVL_CACHE),
      },
    });

    return c15t.handler(request);
  },
};
```

## Custom Cache Adapter

Implement the `CacheAdapter` interface to use any cache backend:

```ts
import type { CacheAdapter } from '@c15t/backend/cache';

const customCache: CacheAdapter = {
  async get<T>(key: string): Promise<T | null> {
    // retrieve from your cache
  },
  async set<T>(key: string, value: T, ttlMs?: number): Promise<void> {
    // store in your cache
  },
  async delete(key: string): Promise<void> {
    // remove from cache
  },
  async has(key: string): Promise<boolean> {
    // check existence
  },
};
```