Cloudflare Workers KV
Globally-distributed, eventually-consistent key-value store optimized for high read volume and low latency.
Overview
KV provides:
- Eventual consistency (60s global propagation)
- Read-optimized performance
- 25 MiB value limit per key
- Auto-replication to Cloudflare edge
- Metadata support (1024 bytes)
Use cases: Config storage, user sessions, feature flags, caching, A/B testing
When to Use KV
| Need | Recommendation |
|---|---|
| Strong consistency | → Durable Objects |
| SQL queries | → D1 |
| Object storage (files) | → R2 |
| High read, low write volume | → KV ✅ |
| Sub-10ms global reads | → KV ✅ |
Quick comparison:
| Feature | KV | D1 | Durable Objects |
|---|---|---|---|
| Consistency | Eventual | Strong | Strong |
| Read latency | <10ms | ~50ms | <1ms |
| Write limit | 1/s per key | Unlimited | Unlimited |
| Use case | Config, cache | Relational data | Coordination |
Quick Start
wrangler kv namespace create MY_NAMESPACE
# Add binding to wrangler.jsonc// Write
await env.MY_KV.put("key", "value", { expirationTtl: 300 });
// Read
const value = await env.MY_KV.get("key");
const json = await env.MY_KV.get<Config>("config", "json");Core Operations
| Method | Purpose | Returns |
|---|---|---|
get(key, type?) |
Single read | string | null |
get(keys, type?) |
Bulk read (≤100) | Map<string, T | null> |
put(key, value, options?) |
Write | Promise<void> |
delete(key) |
Delete | Promise<void> |
list(options?) |
List keys | { keys, list_complete, cursor? } |
getWithMetadata(key) |
Get + metadata | { value, metadata } |
Consistency Model
- Write visibility: Immediate in same location, ≤60s globally
- Read path: Eventually consistent
- Write rate: 1 write/second per key (429 on exceed)
Reading Order
| Task | Files to Read |
|---|---|
| Quick start | README → configuration.md |
| Implement feature | README → api.md → patterns.md |
| Debug issues | gotchas.md → api.md |
| Batch operations | api.md (bulk section) → patterns.md |
| Performance tuning | gotchas.md (performance) → patterns.md (caching) |
In This Reference
- configuration.md - wrangler.jsonc setup, namespace creation, TypeScript types
- api.md - KV methods, bulk operations, cacheTtl, content types
- patterns.md - Caching, sessions, rate limiting, A/B testing
- gotchas.md - Eventual consistency, concurrent writes, value limits
See Also
- workers - Worker runtime for KV access
- d1 - Use D1 for strong consistency needs
- durable-objects - Strongly consistent alternative