Concurrency and Load considerations for Custom Entity creation

Hello everyone,

We intend to create a new entity to store records for a custom requirement for our application.

we seek opinion on the following lines -

If we intend to store ~12,80,000 records, how much of an impact does the Get Document by Id operation suffer ?
(we are trying to simulate ourselves too, but seeking if someone has experience already with these kind of numbers)

Will concurrency be handled as well for simulatenous fetch for same document for update.

Does anyone have experience implementing something similar, anything you can share from your experience would be helpful.

this is an update for anyone else looking for information along the same lines -

We did this poc ourselves and found satisfactory results along the following lines -

We added around 200k+ records with more than 6 fields per entry with a mix of fields like date, string, boolean and number.

Fetching by Id took at an average <= 250 ms.