KV Storage

Cloudflare Workers KV is a global key-value store optimized for read-heavy workloads. Quickback uses KV for session storage, caching, and fast lookups.

What is KV?

Workers KV is a distributed key-value store:

Global distribution - Data replicated to 300+ edge locations
Low-latency reads - Cached at the edge, sub-millisecond access
Eventually consistent - Writes propagate globally within 60 seconds
Simple API - Get, put, delete, list

Use Cases in Quickback

Use Case	Description
Sessions	Better Auth stores sessions in KV for fast validation
Cache	Cache expensive database queries or API responses
Rate Limiting	Track request counts per user/IP
Feature Flags	Store configuration that changes infrequently

Namespace Setup

Create a KV namespace via Wrangler:

# Create namespace
wrangler kv namespace create "SESSIONS"

# Output:
# Add the following to your wrangler.toml:
# [[kv_namespaces]]
# binding = "SESSIONS"
# id = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

Add to wrangler.toml:

[[kv_namespaces]]
binding = "SESSIONS"
id = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

[[kv_namespaces]]
binding = "CACHE"
id = "yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy"

Reading and Writing Values

Basic Operations

// Write a value
await env.CACHE.put("user:123", JSON.stringify({ name: "Alice" }));

// Read a value
const data = await env.CACHE.get("user:123");
const user = data ? JSON.parse(data) : null;

// Delete a value
await env.CACHE.delete("user:123");

// Check if key exists
const exists = await env.CACHE.get("user:123") !== null;

With Metadata

KV supports metadata attached to keys:

// Write with metadata
await env.CACHE.put("user:123", JSON.stringify(userData), {
  metadata: { updatedAt: Date.now(), version: 1 },
});

// Read with metadata
const { value, metadata } = await env.CACHE.getWithMetadata("user:123");

List Keys

// List all keys with prefix
const list = await env.CACHE.list({ prefix: "user:" });

for (const key of list.keys) {
  console.log(key.name, key.metadata);
}

// Paginate through results
let cursor = undefined;
do {
  const result = await env.CACHE.list({ prefix: "user:", cursor });
  // Process result.keys
  cursor = result.cursor;
} while (cursor);

Expiration and TTL

Set automatic expiration on keys:

// Expire in 1 hour (3600 seconds)
await env.CACHE.put("session:abc", sessionData, {
  expirationTtl: 3600,
});

// Expire at specific timestamp
await env.CACHE.put("session:abc", sessionData, {
  expiration: Math.floor(Date.now() / 1000) + 3600,
});

Common TTL patterns:

Use Case	TTL
Session tokens	24 hours (86400)
API cache	5 minutes (300)
Rate limit counters	1 minute (60)
Feature flags	No expiration

Session Storage

Better Auth uses KV for session storage in Cloudflare deployments:

// Quickback configures this automatically
auth: defineAuth("better-auth", {
  session: {
    storage: "kv", // Uses SESSIONS namespace
  },
}),

Sessions are stored as:

Key: session:{sessionId}
Value: Serialized session object
TTL: Configured session expiration

Caching Patterns

Cache-Aside Pattern

async function getUser(userId: string) {
  // Check cache first
  const cached = await env.CACHE.get(`user:${userId}`);
  if (cached) {
    return JSON.parse(cached);
  }

  // Fetch from database
  const user = await db.select().from(users).where(eq(users.id, userId));

  // Store in cache
  await env.CACHE.put(`user:${userId}`, JSON.stringify(user), {
    expirationTtl: 300, // 5 minutes
  });

  return user;
}

Cache Invalidation

// Invalidate on update
async function updateUser(userId: string, data: UserUpdate) {
  await db.update(users).set(data).where(eq(users.id, userId));
  await env.CACHE.delete(`user:${userId}`);
}

wrangler.toml Reference

# Production namespace
[[kv_namespaces]]
binding = "SESSIONS"
id = "abc123..."

# Preview namespace (for wrangler dev)
[[kv_namespaces]]
binding = "SESSIONS"
id = "def456..."
preview_id = "ghi789..."

Limitations

Value size - Maximum 25 MB per value
Key size - Maximum 512 bytes
Write limits - 1 write per second per key
Eventual consistency - Changes may take up to 60 seconds to propagate
Not for hot writes - Use Durable Objects for high-write scenarios

KV is optimized for read-heavy workloads. For write-heavy use cases or strong consistency, consider Durable Objects.

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