As a company grows, it collects tools: a website with forms, a CRM, a payment service, messengers, accounting software and a dozen spreadsheets. Each tool is useful, but together they create duplicated data, manual copying and questions like "which number is correct?".
Decide where the truth lives
For every important type of data - customers, orders, payments, products - choose one system that is the source of truth. Other systems may show or use this data, but changes are made in one place. Without this rule integrations start overwriting each other and nobody trusts the numbers.
Draw the data flows
Before writing code, draw a simple map: which event happens where, which data it produces and where that data must go. For example: a request from the website form creates a lead in the CRM, sends a notification to the manager’s messenger and adds a row to the report. This picture quickly reveals gaps and unnecessary steps.
Plan for failures
Any external service is sometimes unavailable. A reliable integration does not lose data when that happens: it queues the event, retries later and records what went wrong. It should also be safe to repeat - receiving the same event twice must not create two orders.
Watch it working
Integrations break quietly: a partner changes a field, a token expires, a limit is reached. Simple monitoring - a log of processed events, alerts on repeated errors and a daily check that the numbers in different systems match - turns silent failures into problems you can fix in minutes.
Keep it documented
Write down what is connected to what, which accounts and keys are used and who is responsible. When the person who built the integration is on holiday, this short document is what keeps the business running.
The short version
Choose one source of truth for each type of data, map the flows, design for failures and repeats, and monitor the result. Integrations then become a quiet backbone of the business instead of a source of confusion.