@John Wong Yek Hon Thanks for reaching out. Regarding your specific question about whether the cap applies to topics and queues only, or if it also includes subscriptions inside the topics:
The cap of 1,000 entities per messaging unit applies to all entities, including topics, queues, and subscriptions. Therefore, in your case, if you have 3 topics and each topic contains 500 subscriptions, you would have a total of 1,503 entities (3 topics + 1,500 subscriptions).
Given this, you would need 2 messaging units (MUs) to accommodate all your entities, as 1 MU can support up to 1,000 entities.
I hope this clarifies your query. If you have any further questions or need additional assistance, please let me know!