™Technology
What is systems integration?
Integration is getting two systems that were never designed for each other to agree on what the data means.
By Tomryn ·
Most organisations run several systems that each hold part of the truth: a quoting tool, a scheduling system, an accounting package, maybe a spreadsheet that nobody admits to. Integration is the work of connecting them so information is entered once and stays consistent.
The technical mechanics are usually the easy part. The difficulty is almost always that the two systems disagree about what a customer is, or when a job counts as complete.
Common approaches
- Direct API calls between systems, suitable when both offer decent APIs and volume is modest.
- Event-driven messaging, where one system publishes changes and others react, more resilient, more to operate.
- Scheduled batch synchronisation, still the right answer when near-real-time is not needed.
- A middle layer that owns the mapping between systems, useful once there are more than two or three.
Where integrations fail
- Identity: the same customer exists twice, under slightly different names, in two systems.
- Ordering: updates arrive out of sequence and the older one overwrites the newer.
- Partial failure: half the operation succeeded and there is no defined way to recover.
- Silent drift: nobody notices the sync stopped three weeks ago because nothing visibly broke.
- Schema change: the other system adds a field, or changes one, without warning.
What to decide before writing any code
- Which system is authoritative for each piece of information.
- What happens when the two disagree.
- How quickly changes actually need to propagate, the honest answer is rarely 'instantly'.
- How a failed sync becomes visible to a person.
- What gets logged, so that a discrepancy can be traced afterwards.
A note on scope
Integration projects expand naturally, because once data is flowing everyone can think of another thing to connect. The engagements that finish are the ones that defined a small first scope, got it running reliably, and then extended it.