How to Integrate Your CRM, ERP, and Custom Applications
Key takeaway
Start by naming the system of record for every shared entity (customer, order, invoice), then pick the simplest pattern that satisfies your latency needs — scheduled sync for reporting, event-driven webhooks for workflow, direct API calls only for true real-time reads.
Integration projects rarely fail on technology. They fail because two systems each believe they own the customer record, and nobody decided which one wins. Get the data-ownership questions right and the engineering is routine.
Step 1 — Declare a system of record per entity
For each shared object, write down one owner: the CRM owns contacts and opportunities, the ERP owns invoices and inventory, the custom app owns in-product usage. Everything else holds a copy, and copies are never edited directly. This single decision eliminates most sync conflicts before they exist.
Step 2 — Pick the integration pattern that fits the need
- Scheduled batch sync — nightly or hourly. Cheapest and most forgiving; fine for reporting and finance.
- Event-driven (webhooks or a message queue) — a change in one system publishes an event others react to. Best for workflow automation where minutes matter.
- Direct API call at read time — no copy at all. Use it when data must be current to the second and the source system can take the traffic.
- File exchange (SFTP/CSV) — still the right answer for legacy partners that offer nothing else.
Step 3 — iPaaS or custom middleware?
An integration platform (Zapier, Make, Workato, Azure Logic Apps) is the right call for a handful of standard connectors and simple field mapping — it's fast to stand up and easy for operations staff to change. Custom middleware earns its keep when you need non-trivial transformation, idempotency guarantees, retry and replay of failed events, or volumes where per-task pricing gets expensive.
A common mature setup is both: an iPaaS for long-tail SaaS connections, and a small service you own for the two or three high-volume, business-critical flows.
The details that decide whether it survives
- Idempotency — every consumer must tolerate the same message twice, because it will get it twice.
- A dead-letter queue plus an alert; silent failures are the norm otherwise.
- Field-level mapping documentation, versioned with the code.
- Rate-limit awareness — most SaaS APIs will throttle a full re-sync.
- A replay path so you can re-run a day's events after an outage.