One tenant sends you a flood of traffic, that you might not be scaled to handle. Let’s say your application servers are scaled for this traffic, but your single, shared database is not. All that traffic could cause an outage on your database. If this happens, the impact won’t necessarily be on one tenants but all tenants.
There are ways you can mitigate this. Strong isolation is one. Throttling tenant calls could be another.
We don’t know your specific use case enough, but it’s something to think about now.
This is generally referred to as the noisy neighbor problem.
https://docs.aws.amazon.com/wellarchitected/latest/saas-lens...
