customerio-rate-limits

# Customer.io Rate Limits ## Overview Understand Customer.io's API rate limits and implement proper throttling: token bucket limiters, exponential backoff with jitter, queue-based processing, and 429 response handling. ## Rate Limit Reference | API | Endpoint | Limit | Scope | |-----|----------|-------|-------| | Track API | `identify`, `track`, `trackAnonymous` | ~100 req/sec | Per workspace | | Track API | Batch operations | ~100 req/sec | Per workspace | | App API | Transactional email/push | ~100 req/sec | Per workspace | | App API | Broadcasts, queries | ~10 req/sec | Per workspace | These are approximate. Customer.io uses sliding window rate limiting. When exceeded, you get a `429 Too Many Requests` response. ## Instructions ### Step 1: Token Bucket Rate Limiter ```typescript // lib/rate-limiter.ts export class TokenBucket { private tokens: number; private lastRefill: number; constructor( private readonly maxTokens: number = 80, // Stay under 100/sec limit private readonly refillRate: number = 80 // Tokens per second ) { this.tokens = maxTokens; this.lastRefill = Date.now(); } private refill(): void { const now = Date.now(); const elapsed = (now - this.lastRefill) / 1000; this.tokens = Math.min(this.maxTokens, this.tokens + elapsed * this.refillRate); this.lastRefill = now; } async acquire(): Promise<void> { this.refill(); if (this.tokens >= 1) { this.tokens -= 1; return; } // Wait...