scale

name	scale
description	Recommend sharding, caching strategies, and read-replication patterns for Cloudflare architectures. Use this skill when preparing for growth, hitting limits, or optimizing for high traffic.

Cloudflare Scaling Skill

Strategies for scaling Cloudflare architectures beyond default limits while maintaining cost efficiency.

Scaling Decision Matrix

Bottleneck	Symptom	Solution
D1 read latency	>50ms queries	Add KV cache layer
D1 write throughput	Queue backlog	Batch writes, add queue buffer
D1 storage	Approaching 10GB	Archive to R2, partition tables
KV read latency	Cache misses	Key prefixing, predictable keys
KV write rate	1 write/sec/key limit	Shard keys, batch writes
R2 throughput	Slow uploads	Presigned URLs, multipart
Worker memory	128MB limit	Streaming, chunked processing
Worker CPU	30s timeout	Queues, Workflows, DO
Subrequests	1000/request limit	Service Bindings RPC
Queue throughput	Consumer lag	Increase concurrency, batch size

Caching Strategies

Cache Hierarchy

Request → Edge Cache → KV Cache → D1 → Origin
           (Tiered)    (Global)   (Primary)

KV Cache Patterns

Write-Through Cache

async function getWithCache<T>(
  kv: KVNamespace,
  db: D1Database,
  key: string,
  query: () => Promise<T>,
  ttl: number = 3600
): Promise<T> {
  // Try cache first
  const cached = await kv.get(key, 'json');
  if (cached !== null) {
    return cached as T;
  }

  // Cache miss - fetch from D1
  const fresh = await query();

  // Write to cache (non-blocking)
  kv.put(key, JSON.stringify(fresh), { expirationTtl: ttl });

  return fresh;
}

Cache Invalidation

// Pattern 1: TTL-based (simple, eventual consistency)
await kv.put(key, value, { expirationTtl: 300 }); // 5 min

// Pattern 2: Version-based (immediate, more complex)
const version = await kv.get('cache:version');
const key = `data:${id}:v${version}`;

// Invalidate by incrementing version
await kv.put('cache:version', String(Number(version) + 1));

// Pattern 3: Tag-based (flexible, requires cleanup)
await kv.put(`user:${userId}:profile`, data);
await kv.put(`user:${userId}:settings`, settings);

// Invalidate all user data
const keys = await kv.list({ prefix: `user:${userId}:` });
for (const key of keys.keys) {
  await kv.delete(key.name);
}

Tiered Cache (Cloudflare CDN)

Enable in Worker for static-like responses:

// Cache API for fine-grained control
const cache = caches.default;

app.get('/api/products/:id', async (c) => {
  const cacheKey = new Request(c.req.url);

  // Check cache
  const cached = await cache.match(cacheKey);
  if (cached) {
    return cached;
  }

  // Fetch fresh data
  const product = await getProduct(c.env.DB, c.req.param('id'));

  const response = c.json(product);
  response.headers.set('Cache-Control', 's-maxage=300');

  // Store in cache
  c.executionCtx.waitUntil(cache.put(cacheKey, response.clone()));

  return response;
});

Sharding Strategies

Key-Based Sharding (KV)

When hitting 1 write/sec/key limit:

// Problem: High-frequency counter
await kv.put('page:views', views); // Limited to 1/sec

// Solution: Shard across multiple keys
const SHARD_COUNT = 10;

async function incrementCounter(kv: KVNamespace, key: string) {
  const shard = Math.floor(Math.random() * SHARD_COUNT);
  const shardKey = `${key}:shard:${shard}`;

  const current = Number(await kv.get(shardKey)) || 0;
  await kv.put(shardKey, String(current + 1));
}

async function getCounter(kv: KVNamespace, key: string): Promise<number> {
  let total = 0;
  for (let i = 0; i < SHARD_COUNT; i++) {
    const value =  kv.();
    total += (value) || ;
  }
   total;
}

Time-Based Sharding (D1)

For high-volume time-series data:

-- Partition by month
CREATE TABLE events_2025_01 (
    id TEXT PRIMARY KEY,
    timestamp TEXT NOT NULL,
    data TEXT
);

CREATE TABLE events_2025_02 (
    id TEXT PRIMARY KEY,
    timestamp TEXT NOT NULL,
    data TEXT
);

-- Query router in code
function getEventsTable(date: Date): string {
  const year = date.getFullYear();
  const month = String(date.getMonth() + 1).padStart(2, '0');
  return `events_${year}_${month}`;
}

Entity-Based Sharding (D1)

For multi-tenant applications:

// Tenant-specific D1 databases
interface Bindings {
  DB_TENANT_A: D1Database;
  DB_TENANT_B: D1Database;
  // Or use Hyperdrive for external Postgres
}

function getDbForTenant(env: Bindings, tenantId: string): D1Database {
  const dbMapping: Record<string, D1Database> = {
    'tenant-a': env.DB_TENANT_A,
    'tenant-b': env.DB_TENANT_B,
  };
  return dbMapping[tenantId] ?? env.DB_DEFAULT;
}

Read Replication Patterns

D1 Read Replicas

D1 automatically creates read replicas. Optimize access:

// Enable Smart Placement in wrangler.jsonc
{
  "placement": { "mode": "smart" }
}

// Worker runs near data, reducing latency

Multi-Region with Durable Objects

For global coordination with regional caching:

// Durable Object for region-local state
export class RegionalCache {
  private state: DurableObjectState;
  private cache: Map<string, { value: unknown; expires: number }>;

  constructor(state: DurableObjectState) {
    this.state = state;
    this.cache = new Map();
  }

  async fetch(request: Request): Promise<Response> {
    const url = new URL(request.url);
    const key = url.searchParams.get('key');

    if (request.method === 'GET' && key) {
      const cached = this.cache.get(key);
      if (cached && cached.expires > Date.now()) {
        return Response.({ : cached., :  });
      }
       .({ : , :  });
    }

     (request. ===  && key) {
       { value, ttl } =  request.();
      ..(key, {
        value,
        : .() + (ttl * ),
      });
       .({ :  });
    }

     .({ :  }, { :  });
  }
}

Eventual Consistency Pattern

For data that can tolerate staleness:

interface CacheEntry<T> {
  data: T;
  cachedAt: number;
  staleAfter: number;
  expireAfter: number;
}

async function getWithStaleWhileRevalidate<T>(
  kv: KVNamespace,
  key: string,
  fetcher: () => Promise<T>,
  options: {
    staleAfter: number;  // Serve stale, revalidate in background
    expireAfter: number; // Force fresh fetch
  }
): Promise<T> {
  const cached = await kv.get<CacheEntry<T>>(key, 'json');
  const now = Date.now();

  if (cached) {
    // Fresh - return immediately
    if (now < cached.staleAfter) {
      return cached.data;
    }

    // Stale but not expired - return stale, revalidate async
    if (now < cached.expireAfter) {
      // Background revalidation
      kv.put(key, JSON.stringify(await buildCacheEntry(fetcher, options)));
       cached.;
    }
  }

  
   entry =  (fetcher, options);
   kv.(key, .(entry));
   entry.;
}

  buildCacheEntry<T>(
  :  <T>,
  : { : ; :  }
): <<T>> {
   now = .();
   {
    :  (),
    : now,
    : now + options.,
    : now + options.,
  };
}

Queue Scaling

Horizontal Scaling (Concurrency)

{
  "queues": {
    "consumers": [
      {
        "queue": "events",
        "max_batch_size": 100,     // Max messages per invocation
        "max_concurrency": 20,     // Parallel consumer instances
        "max_retries": 1,
        "dead_letter_queue": "events-dlq"
      }
    ]
  }
}

Batch Processing Optimization

export default {
  async queue(batch: MessageBatch, env: Bindings) {
    // Group messages for efficient D1 batching
    const byType = new Map<string, unknown[]>();

    for (const msg of batch.messages) {
      const type = msg.body.type;
      if (!byType.has(type)) byType.set(type, []);
      byType.get(type)!.push(msg.body.payload);
    }

    // Process each type as a batch
    for (const [type, payloads] of byType) {
      await processBatch(type, payloads, env);
    }

    // Ack all at once
    batch.ackAll();
  },
};

async function processBatch(
  type: string,
  payloads: unknown[],
  env: 
) {
  
    = ;
   ( i = ; i < payloads.; i += ) {
     chunk = payloads.(i, i + );
     (env., , chunk);
  }
}

Memory Management

Streaming for Large Payloads

// Problem: Loading entire file into memory
const data = await r2.get(key);
const json = await data.json(); // May exceed 128MB

// Solution: Stream processing
app.get('/export/:key', async (c) => {
  const object = await c.env.R2.get(c.req.param('key'));
  if (!object) return c.json({ error: 'Not found' }, 404);

  return new Response(object.body, {
    headers: {
      'Content-Type': object.httpMetadata?.contentType ?? 'application/octet-stream',
      'Content-Length': String(object.size),
    },
  });
});

Chunked Processing with Durable Objects

// For files >50MB, process in chunks with checkpointing
export class ChunkedProcessor {
  private state: DurableObjectState;

  async processFile(r2Key: string, chunkSize: number = 1024 * 1024) {
    // Get checkpoint
    let offset = (await this.state.storage.get<number>('offset')) ?? 0;

    const object = await this.env.R2.get(r2Key, {
      range: { offset, length: chunkSize },
    });

    if (!object) {
      // Processing complete
      await this.state.storage.delete('offset');
      return { complete: true };
    }

    // Process chunk
    await this.processChunk(await object.());

    
     ...(, offset + chunkSize);

    
     ...(.() + );

     { : , : offset + chunkSize };
  }
}

Scaling Checklist

Before Launch

• KV cache layer for hot data
• D1 indexes on all query columns
• Queue DLQs configured
• Smart Placement enabled
• Batch size ≤1000 for D1 writes

At 10K req/day

• Monitor D1 query performance
• Review cache hit rates
• Check queue consumer lag

At 100K req/day

• Add Analytics Engine for metrics (free)
• Consider key sharding for hot KV keys
• Review batch processing efficiency

At 1M req/day

• Implement Tiered Cache
• Add read-through caching
• Consider time-based D1 partitioning
• Review and optimize indexes

At 10M req/day

• Multi-region strategy
• Entity-based sharding
• Durable Objects for coordination
• Custom rate limiting

Cost Implications

Scaling Strategy	Additional Cost	When to Use
KV caching	$0.50/M reads	D1 read heavy
Key sharding	More KV reads	>1 write/sec/key
Time partitioning	None (same D1)	>10GB data
Tiered Cache	None (CDN)	Cacheable responses
DO coordination	CPU time	Global state
Queue scaling	Per message	High throughput

Anti-Patterns

Pattern	Problem	Solution
Cache everything	KV costs add up	Cache hot data only
Shard too early	Complexity without benefit	Monitor first
Ignore TTLs	Stale data	Set appropriate TTLs
Skip DLQ	Lost messages	Always add DLQ
Over-replicate	Cost multiplication	Right-size replication