Most new business apps are not built in isolation. They have to read from an old ERP, push data to an accounting package, or sync with a third-party platform. The integration layer is where many projects slip, because it is planned last.
Here is a practical checklist to work through when a new web app, SaaS product or mobile app has to talk to existing systems.
1. Map every system before you design endpoints
- List each system the new product must exchange data with: legacy apps, department tools, third-party platforms
- For each one, note the direction of data (in, out or both) and how often it moves
- Decide which system is the source of truth for each data type
2. Make the API layer secure by default
- Authenticate every call, including internal service-to-service traffic
- Give each integration the least access it needs
- Keep secrets out of source code and rotate them on a schedule
- Keep an inventory of every API you expose, and retire the ones nobody calls
3. Keep the architecture modular
- Put each integration behind its own module or adapter, so replacing a legacy system later does not mean rewriting the app
- Run integration tests in your CI/CD pipeline, not just unit tests
- Add monitoring and alerts on integration failures, since a silent sync failure can go unnoticed for days
4. Plan for the dashboard question
If managers will want role-based dashboards, the data model and access rules need to support that from the start. Bolting reporting onto a system that was never designed for it is painful.
More detail: how we approach custom web, SaaS and mobile product engineering
Written by the team at Affix Center, an IT services company in Lower Parel, Mumbai.
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