What is systems integration, and when do you need it?

Someone maintains a spreadsheet that exists only to reconcile two systems. A customer's address is right in one tool and wrong in another. Nobody can answer a simple question about last month without pulling three exports. Month-end takes a week because the numbers have to be assembled by hand.

Every one of those is the same underlying problem: no system owns the fact, so all of them hold a version of it.

First we decide the system of record for each piece of data. The CRM owns the customer, the scheduling tool owns the job, accounting owns the invoice. Everything else receives copies and is never edited directly. That decision is most of the work, and skipping it is why integrations turn into two systems overwriting each other.

Then the connections get built against documented APIs, with retries, logging, and alerts. An integration nobody is watching is a liability, because the failure mode is silence rather than an error message.

This is common in trade and field software. The options are a scheduled file exchange, a screen-driven script, or a supported export the vendor already offers and does not advertise. We look for the last one first, because it is the only one that survives a vendor update.

Whichever route it takes, the bridge gets monitored. A silent failure should reach us as an alert, not reach you as a missing invoice.