flyio-rate-limits

Fly.io Rate Limits

Overview

The Fly.io Machines API rate-limits per organization, with write operations (create, delete, update) throttled much more aggressively than reads. Deploying fleets of edge machines across multiple regions can easily trigger 429s, especially during rolling deployments or auto-scaling events. The API returns a Retry-After header on rate-limited responses, and organizations running 50+ machines should implement client-side token bucket limiting to avoid cascading failures during high-churn operations.

Rate Limit Reference

Endpoint	Limit	Window	Scope
Machine create/delete	10 req	1 minute	Per org
Machine start/stop	30 req	1 minute	Per org
Machine list/get	120 req	1 minute	Per org
App create/delete	5 req	1 minute	Per org
Volume operations	15 req	1 minute	Per org

Rate Limiter Implementation

class FlyRateLimiter {
  private tokens: number;
  private lastRefill: number;
  private readonly max: number;
  private readonly refillRate: number;
  private queue: Array<{ resolve: () => void }> = [];

  constructor(maxPerMinute: number) {
    this.max = maxPerMinute;
    this.tokens = maxPerMinute;
    this.lastRefill = Date.now();
    this.refillRate = maxPerMinute / 60_000;
  }

  async acquire(): Promise<void> {
    this.refill();
    if (this.tokens >= 1) { this.tokens -= 1; return; }
    return new Promise(resolve => this.queue.push({ resolve }));
  }

  private refill() {
    const now = Date.now();
    this.tokens = Math.min(this.max, this.tokens + (now - this.lastRefill) * this.refillRate);
    this.lastRefill = now;
    while (this.tokens >= 1 && this.queue.length) {
      this.tokens -= 1;
      this.queue.shift()!.resolve();
    }
  }
}

const writeLimiter = new FlyRateLimiter(8);  // leave headroom under 10/min
const readLimiter = new FlyRateLimiter(100);

Retry Strategy

async function flyRetry<T>(fn: () => Promise<Response>, maxRetries = 4): Promise<T> {
  for (let attempt = 0; attempt <= maxRetries; attempt++) {
    const res = await fn();
    if (res.ok) return res.json();
    if (res.status === 429) {
      const retryAfter = parseInt(res.headers.get("Retry-After") || "10", 10);
      const delay = retryAfter * 1000 + Math.random() * 2000;
      await new Promise(r => setTimeout(r, delay));
      continue;
    }
    if (res.status >= 500 && attempt < maxRetries) {
      await new Promise(r => setTimeout(r, Math.pow(2, attempt) * 1000));
      continue;
    }
    throw new Error(`Fly API ${res.status}: ${await res.text()}`);
  }
  throw new Error("Max retries exceeded");
}

Batch Processing

async function rollingDeployMachines(appId: string, configs: any[], batchSize = 3) {
  const results: any[] = [];
  for (let i = 0; i < configs.length; i += batchSize) {
    const batch = configs.slice(i, i + batchSize);
    const batchResults = await Promise.all(
      batch.map(async cfg => {
        await writeLimiter.acquire();
        return flyRetry(() =>
          fetch(`https://api.machines.dev/v1/apps/${appId}/machines`, {
            method: "POST", headers, body: JSON.stringify(cfg),
          })
        );
      })
    );
    results.push(...batchResults);
    if (i + batchSize < configs.length) await new Promise(r => setTimeout(r, 10_000));
  }
  return results;
}

Error Handling

Issue	Cause	Fix
429 on machine create	Exceeded 10 writes/min org limit	Use Retry-After header, batch deploys
429 on fleet list	Monitoring polling too fast	Cache responses, poll every 30s max
Timeout on volume attach	Volume in another region	Verify region match before attach
503 during region outage	Specific edge region down	Fail over to secondary region
409 on machine update	Concurrent config change	Re-fetch machine state, retry with latest version

Resources

• Fly.io Machines API

Next Steps

See flyio-performance-tuning.