There's a few. My company has been using serverless aurora pretty much since preview and will keep doing so for some parts of infra, but are moving some services back to provisioned.
- Data is replicated cross region, but your compute all lives in the same AZ, so if (when) an AZ goes down you have to wait for a new instance to be created elsewhere. AWS says the time for this is undefined, IIRC we've seen it be around 15-20 minutes before the DB is back online.
- If you have lots of long running transactions or queries, serverless can have trouble finding a scaling point and won't scale up/down. You can set it to force scaling after 5 attempts, but this results in dropped connections and 1-2 minutes of downtime every time.
- Scaling up actually takes 45s-1:30 for new capacity to be available. If your load is spiky enough that that's too slow, you're stuck with overprovisioning anyways.
- Tools like VividCortex don't work for serverless if you rely on those. Teams here that use serverless have shifted to DataDog APM for this purpose.
- Loading data from S3 doesn't work. This wasn't really a usecase we had but it's something to be aware of.
That said, for gradual load or DB downtime tolerant services it's great! Also very nice for dev environments as the scaling down to 0 can result in some very real cost savings.
- Data is replicated cross region, but your compute all lives in the same AZ, so if (when) an AZ goes down you have to wait for a new instance to be created elsewhere. AWS says the time for this is undefined, IIRC we've seen it be around 15-20 minutes before the DB is back online.
- If you have lots of long running transactions or queries, serverless can have trouble finding a scaling point and won't scale up/down. You can set it to force scaling after 5 attempts, but this results in dropped connections and 1-2 minutes of downtime every time.
- Scaling up actually takes 45s-1:30 for new capacity to be available. If your load is spiky enough that that's too slow, you're stuck with overprovisioning anyways.
- Tools like VividCortex don't work for serverless if you rely on those. Teams here that use serverless have shifted to DataDog APM for this purpose.
- Loading data from S3 doesn't work. This wasn't really a usecase we had but it's something to be aware of.
That said, for gradual load or DB downtime tolerant services it's great! Also very nice for dev environments as the scaling down to 0 can result in some very real cost savings.