HTTP API in realtime vs reports

Please enlighten me here. I find it hard to understand the difference between realtime behaviour and reports.

Scenario: We recently added a custom dimension and a manual JavaScript snippet to track it’s use. I can query Matomo using the HTTP API to see one action for one value of this dimension, but when I go to the reports in the Matomo backend, there’s nothing for this dimension, even after waiting one hour (our update interval is set to 3600). Why this difference between HTTP API and backend? Is it better to create you own reports using the HTTP API than to rely on a broken backend tool?

Nevermind, cronjob was not working properly, and neither date selection in backend.