Are Custom Actions async?

​@Michael_Soprano I had responded to this a few months ago. Let me know if you need any additional details. 

AJO Custom Actions are synchronous from the journey’s perspective.

The journey waits for the API response before moving to the next step, even though the HTTP call is processed asynchronously internally.

• Max timeout typically up to 30s
• For true async processing, return quickly (200/202) and continue later via another event/webhook

https://experienceleague.adobe.com/en/docs/journey-optimizer/using/connect-systems/external-systems/external-systems#timeout