customerio-load-scale

name	customerio-load-scale
description	Implement Customer.io load testing and horizontal scaling. Use when preparing for high traffic, running load tests, or designing queue-based architectures for scale. Trigger: "customer.io load test", "customer.io scale", "customer.io high volume", "customer.io k6", "customer.io performance test".
allowed-tools	Read, Write, Edit, Bash(npm:*), Bash(npx:*), Bash(kubectl:*), Glob, Grep
version	1.14.0
license	MIT
author	Jeremy Longshore <[e-mail]>
tags	["saas","customer-io","load-testing","scaling","performance"]
compatibility	Designed for Claude Code

Customer.io Load & Scale

Overview

Load testing and scaling strategies for high-volume Customer.io integrations: k6 load test scripts, scaling architecture selection based on volume tier, Kubernetes HPA autoscaling, message queue buffering, and rate-limit-aware batch processing.

Scaling Architecture by Volume

Daily Events	Architecture	Key Components
< 100K	Direct API	Singleton client, retry, connection pooling
100K - 1M	Batched API	Event queue, batch processor, rate limiter
1M - 10M	Queue-backed	Redis/Kafka queue, worker pool, backpressure
> 10M	Distributed	Multiple workspaces, sharded queues, regional routing

Customer.io rate limit is ~100 req/sec per workspace. Plan your architecture around this.

Instructions

Step 1: k6 Load Test Script

// load-tests/customerio.js
// Run: k6 run --vus 10 --duration 60s load-tests/customerio.js
import http from "k6/http";
import { check, sleep } from "k6";
import { Counter, Trend } from "k6/metrics";

const SITE_ID = __ENV.CUSTOMERIO_SITE_ID;
const API_KEY = __ENV.CUSTOMERIO_TRACK_API_KEY;
const BASE_URL = "https://track.customer.io/api/v1";
const AUTH = `${SITE_ID}:${API_KEY}`;

const identifyLatency =  ();
 trackLatency =  ();
 errors =  ();

  options = {
  : {
    : {
      : ,
      : ,
      : ,
      : ,
      : ,
      : [
        { : , :  },   
        { : , :  },   
        { : , :  },   
      ],
    },
  },
  : {
    : [, ],
    : [, ],
    : [],
  },
};

   () {
   userId = ;
   headers = {
    : ,
    : ,
  };

  
   identifyRes = http.(
    ,
    .({
      : ,
      : ,
      : .(.() / ),
    }),
    { headers }
  );

  identifyLatency.(identifyRes..);
  (identifyRes, { :  r. ===  }) || errors.();

  
   trackRes = http.(
    ,
    .({
      : ,
      : { : __ITER, : __VU },
    }),
    { headers }
  );

  trackLatency.(trackRes..);
  (trackRes, { :  r. ===  }) || errors.();

  (); 
}


  () {
  .();
}