Klaviyo Reference Architecture

Overview

Production-ready architecture for Klaviyo integrations: a layered project structure, service patterns, event-driven sync, and the klaviyo-api SDK wired into a real application. SKILL.md gives you the four-layer contract and the skeleton you scaffold from; the deep material lives in references/ so you pull code only when you reach that layer.

• Layout & layering (full directory tree, layer contract, data flow): architecture.md
• Working code for every layer (config, profile sync, event tracker): implementation.md

Prerequisites

• TypeScript project with klaviyo-api installed
• Understanding of layered architecture
• Redis (for caching/queuing) and database (for audit/sync state)

Instructions

Use Write to scaffold the directory tree, then fill each layer bottom-up. The four layers and their one-way call rule:

API / Webhook Layer   →  routes + webhook handlers (calls Service only)
Service Layer         →  profile-sync, event-tracker, campaigns (calls SDK + Infra)
Klaviyo SDK Layer     →  ApiKeySession, ProfilesApi, EventsApi (never calls upward)
Infrastructure Layer  →  Redis cache, BullMQ queue, Prisma DB, OTel monitoring

1. Scaffold the tree. Create the src/{klaviyo,services,webhooks,jobs,middleware,config,health} layout. Full annotated tree: architecture.md.
2. Config layer first. A single loadConfig() returns environment-specific keys, rate limits, and cache TTLs — every other layer reads from it. Code: implementation.md Step 1.
3. Service layer. Build ProfileSyncService (bidirectional upsert) and EventTracker (server-side Placed Order / custom events). Both route Klaviyo calls through withRateLimitRetry. Code: implementation.md Steps 2–3.
4. Wire the data flow. Signup → syncToKlaviyo(), purchase → trackPurchase(), inbound profile.updated webhook → WebhookRouter.routeEvent() → local DB. Diagram: architecture.md.

When reviewing an existing project, Read its src/ tree and Grep for cross-layer imports that break the one-way rule (SDK importing a service, a route importing the SDK directly).

Output

Applying this skill produces:

• A scaffolded src/ tree matching the four-layer contract, with SDK, service, webhook, job, middleware, config, and health directories.
• A working config/klaviyo.ts plus ProfileSyncService and EventTracker service classes ready to call from routes and jobs.
• For a review pass: a list of layering violations (upward SDK calls, direct SDK use from routes) and sync-safety gaps to fix.

Error Handling

Issue	Cause	Solution
Circular deps	Wrong layering	Services call SDK, never the reverse
Sync conflicts	Both sides update	Last-write-wins with sync timestamp
Queue backlog	Klaviyo slow/down	Circuit breaker + dead letter queue
Type mismatches	SDK version mismatch	Pin SDK version, run tsc --noEmit in CI

Examples

Scaffold a new integration — "Set up a Klaviyo integration for our Node app." Create the layered tree, drop in loadConfig(), then ProfileSyncService and EventTracker. Full code per step: implementation.md.

Track a purchase from your backend:

await new EventTracker().trackPurchase({
  email: order.email,
  orderId: order.id,
  total: order.total,
  items: order.lineItems,
});

Review project structure — "Is our Klaviyo code layered correctly?" Grep for imports that violate the one-way call rule and check webhook handlers verify HMAC signatures. Layer contract: architecture.md.

Resources

• Klaviyo API Reference
• Custom Integration Guide
• Ecommerce Integration Guide

Next Steps

For multi-environment configuration and per-stage key management, see the klaviyo-multi-env-setup skill in this pack.