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

Integrar una base de datos existente a Discourse

what (blox) 17 Julio, 2023 22:03 4

¿Es posible importar más de 500 GB? ¿O hay un límite de tamaño?

Tema		Respuestas	Vistas
Import CSV into Discourse Marketplace	1	1035	11 Abril 2021
Import from self build board? Self-hosting	4	766	2 Abril 2020
Need someone to help me import old forum members and topics! Marketplace	3	1544	25 Enero 2016
[Paid] Migrate proprietary forums to Discourse Marketplace delivered	3	1473	16 Abril 2020
Deeply integrating Discourse into website Development	6	12256	17 Febrero 2022