The short answer
Integration is the single most common reason software estimates are wrong, because the difficulty is invisible until someone tries. Find out which of the three cases you are in before you commit to anything that depends on it.
The three cases
| Case | What it means | Realistic effort |
|---|---|---|
| Documented API | Public developer docs, keys you can generate | Days |
| Undocumented or gated API | It exists; the vendor controls access | Weeks, plus a commercial conversation |
| No API | Nothing to connect to | Scheduled export and import, or manual |
How to find out which one you have, today
Fifteen minutes of research
- Search '[vendor name] API documentation'Public docs mean case one. No docs usually means case two or three.
- Check whether the API is on a higher price tierVery common, and it changes the budget rather than the build.
- Look for an export function in the softwareIf it can produce a CSV on a schedule, case three is workable.
- Ask the vendor directly, in writingAsk specifically whether third-party integration is permitted, not just possible.
Why a nightly export is often the right answer
It sounds like a compromise. Frequently it is the better engineering decision.
Live sync means two systems that must both be available, must agree on state, and must handle failure in the middle of a transaction. A scheduled export means one file, one direction, and a failure mode that is obvious and recoverable.
If your business does not genuinely need up-to-the-second data, do not pay for it.
Common questions
How do I know if my system has an API?
Search the vendor's site for developer documentation. If there is public documentation, integration is likely straightforward. If you have to email sales to ask, expect it to be chargeable, limited, or both.
What if there is no API at all?
Then the honest answer is usually a scheduled export and import: a file dropped somewhere overnight and picked up. It is less elegant than live sync and it works reliably, which matters more.
Why do integrations blow up project estimates?
Because the difficulty is invisible until someone tries. Two systems with good APIs is a day. One system with a closed API and a vendor who will not help can consume a whole project.