618 million Daily Active Users.
4000 shards, 9000 memcache instances.
Simple math, 618m/4000 is 154000 users per database (this is a horrible metric but illustrates my point) and 618m/9000 = 68666 and a bit users per memcache intances.
I hardly think this is a "fate worse than death", When you have a billion users with 600,000,000 DAU's whatever technology you use is going to have snags as you are pushing the envelope in just about every way.
This article reads like a Microsoft Whitepaper about why only a Microsoft technology running on a Microsoft platform will solve all your problems.
Also, full ACID is overrated. Banks do well without it for years.
Previous comments: https://news.ycombinator.com/item?id=2740432
Pretty closed minded approach. Just because it is usually not a good idea to do a rewrite, does not mean it is always true.
Here is an example which indicates you are probably wrong with that type of thinking:
What happens if a shop decides to store all their data in flat text files initially because it was easier and they were not expecting it to scale much. Later on and after huge expansion they realize that flat text files really is not the best solution, in fact it is pretty much the worst solution and decide that a rewrite with better technology is needed.
At this point you say you lose all respect for them? Does that attitude make sense?
Being an engineer myself, I know how easy it is to see things as black and white and that the right answer is "just so obvious." But the more I do, the more I see that this approach is almost always wrong or, at best, half-baked.
In most situations, there is more than one option. So, to say that rewriting everything is the only solution, especially when the guy doesn't even work at Facebook, is a classic example of engineering arrogance.
The second problem I have with the original comment is that it doesn't acknowledge that, in any situation, tradeoffs exist. The way you sell things, both to executives and potential customers, is not to just come in and say "there is only one right answer, you have to do it this way" but to provide a thorough analysis of the current situation, acknowledge the different tradeoffs and provide options based on the top few scenarios.
When a distinguished but elderly scientist states that something is possible,
he is almost certainly right.
When he states that something is impossible, he is very probably wrong.
2.The only way of discovering the limits of the possible
is to venture a little way past them into the impossible.
3.Any sufficiently advanced technology is indistinguishable from magic.