GET_LOCK and database sessions causing issues with AWS serverless database

I think the error relates to serverless being able to scale. So when traffic comes in, it just isn't scaling. AWS support have said the reason for this is locked tables or long running connections. Which made me think that perhaps the sessions were the problem, but that's just a guess. They have said that serverless just isn't going to work for us but haven't been any more helpful than that in working out why exactly.