Klaviyo Rate Limits

Overview

Handle Klaviyo's per-account fixed-window rate limits with proper Retry-After header handling, exponential backoff, and request queuing. This skill installs a small set of composable helpers: a retry wrapper that honors Klaviyo's Retry-After, a request queue that paces sustained throughput, a monitor that reads live rate-limit headers, and a rate-aware bulk import.

Prerequisites

• The klaviyo-api SDK installed in the target project (npm install klaviyo-api).
• The p-queue package installed for the request queue (npm install p-queue).
• A working knowledge of Klaviyo's dual-window (burst + steady) rate limiting, summarized in the architecture table below.
• Write access to the project's src/klaviyo/ directory, where the generated helper files land.

Klaviyo Rate Limit Architecture

Klaviyo uses per-account fixed-window rate limiting with two distinct windows:

Both windows apply simultaneously. Exceeding either triggers a 429 Too Many Requests.

Rate Limit Headers

On successful requests:

On 429 responses (different headers!):

> Critical: When you hit a 429, RateLimit-* headers are NOT returned. Only Retry-After is present.

Instructions

Step 1: Retry-After Aware Backoff (core)

Use Write to create src/klaviyo/rate-limiter.ts with the retry wrapper below. This is the foundation every other helper builds on: it retries only on 429 and 5xx, always honors Klaviyo's Retry-After on a 429, and falls back to exponential backoff with jitter for 5xx.

// src/klaviyo/rate-limiter.ts

export async function withRateLimitRetry<T>(
  operation: () => Promise<T>,
  options = { maxRetries: 5, baseDelayMs: 1000, maxDelayMs: 60000 }
): Promise<T> {
  for (let attempt = 0; attempt <= options.maxRetries; attempt++) {
    try {
      return await operation();
    } catch (error: any) {
      if (attempt === options.maxRetries) throw error;

      const status = error.status;

      // Only retry on 429 (rate limit) and 5xx (server errors)
      if (status !== 429 && (status < 500 || status >= 600)) throw error;

      let delayMs: number;

      if (status === 429) {
        // ALWAYS honor Klaviyo's Retry-After header
        const retryAfter = error.headers?.['retry-after'];
        delayMs = retryAfter
          ? parseInt(retryAfter) * 1000
          : options.baseDelayMs * Math.pow(2, attempt);
      } else {
        // 5xx: exponential backoff with jitter
        const exponential = options.baseDelayMs * Math.pow(2, attempt);
        const jitter = Math.random() * options.baseDelayMs;
        delayMs = Math.min(exponential + jitter, options.maxDelayMs);
      }

      console.log(`[Klaviyo] ${status} on attempt ${attempt + 1}. Retrying in ${delayMs}ms...`);
      await new Promise(r => setTimeout(r, delayMs));
    }
  }
  throw new Error('Unreachable');
}

Steps 2–4: Queue, Monitor, and Bulk operations

Layer the sustained-throughput controls on top of the retry wrapper. Each is a small file you Write into src/klaviyo/; the full annotated code for all three is in the implementation walkthrough:

• Step 2 — Request queue (src/klaviyo/queue.ts): a p-queue capped at 60 req/s (headroom under the 75 req/s burst wall) that wraps every call in withRateLimitRetry. This prevents most 429s instead of just reacting to them.
• Step 3 — Rate limit monitor (src/klaviyo/monitor.ts): reads the RateLimit-* response headers so throttle decisions track the account's real remaining budget — important when multiple processes share one quota.
• Step 4 — Rate-aware bulk sync (bulkProfileSync): batches large imports through the queue and paces between batches so a 100k-profile sync never trips the steady (1-minute) cap.

Read references/implementation.md for the complete source of Steps 2–4, and references/examples.md for end-to-end usage.

Output

Applying this skill produces the following in the target project:

• src/klaviyo/rate-limiter.ts — withRateLimitRetry, the Retry-After-honoring retry wrapper (Step 1).
• src/klaviyo/queue.ts — queuedKlaviyoCall, the paced request queue (Step 2).
• src/klaviyo/monitor.ts — rateLimitMonitor, a live header-driven throttle monitor (Step 3).
• bulkProfileSync — a rate-aware batch import helper (Step 4).

At runtime the helpers emit [Klaviyo] console logs on each retry, batch, and queue-drain event, and bulkProfileSync returns a { success, failed } count so callers can report import results. Net effect: Klaviyo API traffic stays under both the burst and steady windows, and any 429 that does occur is absorbed by honoring Retry-After rather than failing the request.

Error Handling

Examples

Common wirings of the helpers — a single rate-safe call, high-volume writes through the queue, a 100k-profile import, and proactive throttling from live headers — are collected in references/examples.md. The minimal case is one wrapped call:

import { withRateLimitRetry } from './klaviyo/rate-limiter';

const profile = await withRateLimitRetry(() =>
  profilesApi.getProfile('01H...')
);

See the worked examples for Examples 2–4.

Resources

• Klaviyo Rate Limits & Error Handling
• API Overview
• p-queue
• Full implementation walkthrough — Steps 2–4 source
• Worked examples — end-to-end usage patterns

Next Steps

For security configuration, see klaviyo-security-basics.