Cloudflare Workers KV Simulator

Workers KV is a global key-value data store built into Cloudflare's edge network. It is eventually consistent — writes propagate to all edge nodes within ~60 seconds. It is ideal for storing configuration, feature flags, session data, and content that is read frequently and written occasionally.

This simulator runs in-browser memory — data is lost on page refresh. It mimics the Workers KV JavaScript API surface (get, put, delete, list, getWithMetadata) but does not enforce real KV limits (key size: 512 bytes, value size: 25MB, 1,000 keys per list call) and has no propagation delay.

env.MY_KV.get(key) returns the stored string value (or null). env.MY_KV.getWithMetadata(key) returns { value, metadata } where metadata is an optional structured object stored alongside the value. Metadata is useful for storing TTL hints, content types, or any structured data without encoding it in the value string.

KV is best for globally distributed reads with low write frequency. Durable Objects provide strongly consistent, low-latency storage with co-location — good for real-time collaboration, counters, and rate limiting. D1 is a relational SQLite database at the edge — use it when you need SQL queries, joins, and transactions.

expirationTtl sets a TTL in seconds after which the key is automatically deleted. For example, { expirationTtl: 3600 } deletes the key after one hour. Useful for session tokens, rate-limit counters, and temporary data. The minimum TTL is 60 seconds.

Define the binding in your wrangler.toml: [[kv_namespaces]] binding = 'MY_KV' id = 'your-namespace-id'. Then access it in your Worker via env.MY_KV. Run 'wrangler kv:namespace create MY_KV' to create a namespace and get its ID.