Google still only has ~180k employees, and obviously not all of them use figma, and obviously not all of their figma users are performing actions simultaneously. I'd be surprised if it broke 10k QPS (would an org like Google even have 10k peak active user sessions? Seems doubtful). Human generated traffic tends to just not reach that large of scales unless you're trying to fit the entire planet on one instance.

RDS can be absurdly limited with IOPS, granted, but a modern laptop for example ought to be up to the task. Realistically you could probably be fine even on RDS but you might need to pay through the nose for extra IOPS.