When US east was freaking out last year, we found Lambda was unreliable. For days ahead of the outages, Lambda would take many hours to respond to S3 events.

When the events eventually came in and fired an event, the logs reflected the time, hours before, when it should have happened.

Sadly, I don't have a support contract so I couldn't get any help. The forums just assumed I was doing something wrong, until the outage which was linked to dynamo IIRC.

We moved on from lambda as well.