With read replicas multiple can read at the same time, but only one writes at the precise same time.
With read replicas multiple can read at the same time, but only one writes at the precise same time. However, as @Ahz was implying, if your definition of "the same time" is in the same second or 100ms, you could have a number of them satisfy that. D1 is built on Durable Objects (DO) and the general understanding that you can have no more than about 1000 requests per second. With write, I suspect that's much lower, but how much would depend upon your writes.
