AppEngine had some big failures early on, but I (and some friends) built a $$$$$$$$$$$$ company on AppEngine (and GCP) and couldn't have done it without it. The stability the last few years has been extremely good. Our base logic was that we trust Google to hire and train talented DevOps more than we can do it and it sure sucks carrying a pager.
If your app is that big, someone is always carrying a pager for when there are problems. The difference is on PaaS, you can't do a damn thing about it if it's a problem with the platform.
I've helped multiple companies get off of app engine because even for companies losing money (startups), it's too unreliable -- and actually very slow (datastore) if your app is relational. Also, it's very very expensive if you hit the datastore hard.
Not quite, but first MVP in 3 months and $80m gross revenue in the first year. Selling t-shirts. We did it with 3 engineers, no devops or qa teams and definitely no pagers. We had zero downtime and the very rare bugs were fixed on the next push to master (CI/CD) and real testing.
I'm not saying the datastore is perfect, but using the datastore has well known and predictable limitations that need to be engineered for. It is definitely not something you can RTFM later on. Just like any database to be honest. It is not a relational database. It doesn't do aggregations. It is for storing data (using Objectify [0]) and memcache is for caching that data.
