Would it be possible to have a API for another database with its own topics, posts, search and integrate that into Discourse so I can use Discourse as a front end and that as an backend?

No. Think about import your data.

Is it possible to import 500gb+? Or is there a size limit

לשלב בסיס נתונים קיים ל-Discourse

Falco (Falco) 17 ביולי,‏ 2023,‏ 10:21pm 5

No, there is no size limit.

נושא		תגובות	צפיות
Import CSV into Discourse Marketplace	1	1046	11 באפריל,‏ 2021
Import from self build board? Self-hosting	4	804	2 באפריל,‏ 2020
Need someone to help me import old forum members and topics! Marketplace	3	1563	25 בינואר,‏ 2016
[Paid] Migrate proprietary forums to Discourse Marketplace delivered	3	1496	16 באפריל,‏ 2020
Deeply integrating Discourse into website Development	6	12302	17 בפברואר,‏ 2022