System Design for Integrations

Design APIs, event flows, data synchronization, failure recovery, and production operations for systems that must work across organizational boundaries.

What this course is about

Integration system design is the discipline of connecting systems that have different owners, APIs, data models, reliability characteristics, and operational constraints. The challenge is not merely moving data from A to B. A production integration must remain correct when requests time out, events arrive twice or out of order, downstream systems become unavailable, rate limits are reached, or two systems disagree.

This course uses commerce integrations as its main setting because they make those problems concrete: product catalogs, stock levels, customer orders, shipping updates, merchant software, and marketplace APIs. The underlying design methods apply equally to SaaS integrations, enterprise connectors, payment workflows, logistics platforms, and other partner-facing systems.

What you will learn

• Frame an integration by identifying actors, system boundaries, sources of truth, and synchronization direction.
• Choose between REST, webhooks, polling, queues, pub/sub, and synchronous or asynchronous processing.
• Design retry-safe APIs and consumers with idempotency, deduplication, timeouts, backoff, DLQs, and ordering controls.
• Keep large datasets synchronized with pagination, batching, checkpoints, incremental sync, backfill, and reconciliation.
• Protect multi-tenant integrations with OAuth scopes, token lifecycle controls, signatures, replay protection, and tenant isolation.
• Operate integrations using correlation IDs, logs, metrics, traces, alerts, replay tooling, and partner-facing diagnostics.
• Present a complete integration architecture clearly in a system-design interview.

Course structure

The worked example

Module 6 turns the earlier concepts into one connected example. You will design how TikTok Shop can exchange product information, stock levels, customer orders, and shipping updates with the merchant's internal software. The module introduces industry abbreviations only when they become useful and explains each one in plain language. These systems are example actors, not mandatory components of every integration.

How to study it

1. Read Modules 1–5 in order to build the core design vocabulary.
2. Before opening Module 6, sketch your own commerce integration and label every source of truth.
3. Use Module 7 to threat-model the design and separate authentication, authorization, integrity, and tenant isolation.
4. In Module 8, redraw the complete architecture from memory and explain how it handles duplicates, outages, overload, and repair.
5. Answer each quiz before revealing the explanation. In an interview, the reasoning matters more than the letter.