Most real systems aren't built from scratch in a vacuum. They need to talk to something that already exists: a CRM like Salesforce, an ERP like SAP, a legacy system nobody wants to touch, or another team's service. That's where a project actually breaks, not in the new code.

We design APIs and build the integration layer between systems, using the same shape that's worked across the enterprise projects we've owned: a thin edge, a gateway that handles auth, routing and rate limits, a domain service that holds the real business rules, events instead of tight point-to-point coupling (Kafka, RabbitMQ), and a data layer nobody queries directly.

What that covers:

API design, REST or event-driven. Contract-first when a frontend or another team needs to build against it in parallel.
Integration with existing systems (CRM, ERP, legacy platforms), without those systems' constraints leaking into the new codebase.
Idempotent event handling, so a retried message or a duplicate webhook doesn't corrupt data.
Documentation the next engineer can actually use, not a contract sitting in someone's head.

This is the connective layer between systems. It pairs well with custom development or legacy modernization, when the real complexity is in what the system has to talk to rather than in the system itself.

Have a system that needs to integrate with something you don't control? Let's talk.