Spent the last 7 months building the integration layer behind an analytics product that connects to a CRM platform, the part that authenticates, pulls historical data, and keeps everything in sync in real time. Wanted to share a few things that surprised me, since most of this never shows up unless you're the one building underneath it.

The biggest one: pagination silently changed strategy partway through large data pulls. The API would start with page-based pagination and switch to cursor-based mid-sync, with nothing announcing it happened. My first sync just quietly dropped records for a week before the counts stopped adding up and I went looking.

Webhooks lied too, in a specific way. An event would fire, I'd go fetch the record it pointed to, and it wouldn't be there yet. The API lagged behind its own webhook system by a beat. Fixed it with a short deliberate delay before the fetch instead of retrying immediately, which just hammered an endpoint that wasn't ready.

Billing got weirder than expected once it wasn't per-user. When access is billed per account rather than per person, you get real scenarios most billing integrations don't plan for: two team members trying to pay for the same thing at once, a payer's card failing on renewal, responsibility shifting from one person to another without anyone losing access mid-transition.

None of this is visible from the outside. As a CRM user you just experience "the integration is being weird again" with no idea why. Usually it's not that the platform is broken, it's that these tools grow faster than their APIs get documented, and things quietly shift underneath the surface.

Curious if others managing CRM integrations have run into similar flakiness, pagination inconsistency, webhook timing issues, or anything else that only shows up once you're deep in the plumbing.