Customer.io SDK Patterns

Overview

Production-ready patterns for Customer.io SDK usage including error handling, batching, and type safety.

Prerequisites

• Customer.io SDK installed
• TypeScript project (recommended)
• Understanding of async/await patterns

Instructions

Pattern 1: Type-Safe Client

// types/customerio.ts
export interface UserAttributes {
  email: string;
  first_name?: string;
  last_name?: string;
  created_at?: number;
  plan?: 'free' | 'pro' | 'enterprise';
  [key: string]: string | number | boolean | undefined;
}

export interface EventData {
  [key: string]: string | number | boolean | object;
}

export type EventName =
  | 'signed_up'
  | 'subscription_started'
  | 'subscription_cancelled'
  | 'feature_used'
  | 'email_verified';

// lib/customerio-client.ts
import { TrackClient, RegionUS } from '@customerio/track';
import type { UserAttributes, EventData, EventName } from '../types/customerio';

export class TypedCustomerIO {
  private client: TrackClient;

  constructor() {
    this.client = new TrackClient(
      process.env.CUSTOMERIO_SITE_ID!,
      process.env.CUSTOMERIO_API_KEY!,
      { region: RegionUS }
    );
  }

  async identify(userId: string, attributes: UserAttributes): Promise<void> {
    await this.client.identify(userId, {
      ...attributes,
      _updated_at: Math.floor(Date.now() / 1000)
    });
  }

  async track(userId: string, event: EventName, data?: EventData): Promise<void> {
    await this.client.track(userId, { name: event, data });
  }
}

Pattern 2: Retry with Exponential Backoff

// lib/customerio-resilient.ts
import { TrackClient } from '@customerio/track';

interface RetryConfig {
  maxRetries: number;
  baseDelay: number;
  maxDelay: number;
}

const defaultRetryConfig: RetryConfig = {
  maxRetries: 3,
  baseDelay: 1000,
  maxDelay: 10000
};

async function withRetry<T>(
  operation: () => Promise<T>,
  config: RetryConfig = defaultRetryConfig
): Promise<T> {
  let lastError: Error | undefined;

  for (let attempt = 0; attempt <= config.maxRetries; attempt++) {
    try {
      return await operation();
    } catch (error) {
      lastError = error as Error;

      if (attempt === config.maxRetries) break;

      // Don't retry on 4xx errors (client errors)
      if (error instanceof Error && error.message.includes('4')) {
        throw error;
      }

      const delay = Math.min(
        config.baseDelay * Math.pow(2, attempt),
        config.maxDelay
      );
      await new Promise(resolve => setTimeout(resolve, delay));
    }
  }

  throw lastError;
}

export class ResilientCustomerIO {
  private client: TrackClient;

  constructor(siteId: string, apiKey: string) {
    this.client = new TrackClient(siteId, apiKey, { region: RegionUS });
  }

  async identify(userId: string, attributes: Record<string, any>) {
    return withRetry(() => this.client.identify(userId, attributes));
  }

  async track(userId: string, event: string, data?: Record<string, any>) {
    return withRetry(() => this.client.track(userId, { name: event, data }));
  }
}

Pattern 3: Event Queue with Batching

// lib/customerio-queue.ts
interface QueuedEvent {
  userId: string;
  event: string;
  data?: Record<string, any>;
  timestamp: number;
}

export class CustomerIOQueue {
  private queue: QueuedEvent[] = [];
  private flushInterval: NodeJS.Timer | null = null;
  private maxBatchSize = 100;
  private flushIntervalMs = 5000;

  constructor(private client: TrackClient) {
    this.startAutoFlush();
  }

  enqueue(userId: string, event: string, data?: Record<string, any>) {
    this.queue.push({
      userId,
      event,
      data,
      timestamp: Date.now()
    });

    if (this.queue.length >= this.maxBatchSize) {
      this.flush();
    }
  }

  async flush(): Promise<void> {
    if (this.queue.length === 0) return;

    const batch = this.queue.splice(0, this.maxBatchSize);

    await Promise.allSettled(
      batch.map(item =>
        this.client.track(item.userId, {
          name: item.event,
          data: { ...item.data, _queued_at: item.timestamp }
        })
      )
    );
  }

  private startAutoFlush() {
    this.flushInterval = setInterval(() => this.flush(), this.flushIntervalMs);
  }

  async shutdown(): Promise<void> {
    if (this.flushInterval) {
      clearInterval(this.flushInterval);
    }
    await this.flush();
  }
}

Pattern 4: Singleton with Lazy Initialization

// lib/customerio-singleton.ts
import { TrackClient, RegionUS } from '@customerio/track';

let instance: TrackClient | null = null;

export function getCustomerIO(): TrackClient {
  if (!instance) {
    if (!process.env.CUSTOMERIO_SITE_ID || !process.env.CUSTOMERIO_API_KEY) {
      throw new Error('Customer.io credentials not configured');
    }
    instance = new TrackClient(
      process.env.CUSTOMERIO_SITE_ID,
      process.env.CUSTOMERIO_API_KEY,
      { region: RegionUS }
    );
  }
  return instance;
}

// Usage
import { getCustomerIO } from './lib/customerio-singleton';
await getCustomerIO().identify('user-123', { email: 'user@example.com' });

Output

• Type-safe Customer.io client
• Resilient error handling with retries
• Event batching for high-volume scenarios
• Singleton pattern for resource efficiency

Error Handling

Error	Cause	Solution
Type mismatch	Invalid attribute type	Use TypeScript interfaces
Queue overflow	Too many events	Increase flush frequency or batch size
Retry exhausted	Persistent failure	Check network and credentials

Resources

• Customer.io SDK GitHub
• API Rate Limits

Next Steps

After implementing patterns, proceed to

customerio-primary-workflow

to implement messaging workflows.