[lock1]

Wait what? I don't get why performance improvement implies reliability and incident improvement.

For example, doing dangerous thing might be faster (no bound checks, weaker consistency guarantee, etc), but it clearly tend to be a reliability regression.

[spiffyk]

First, if a performance optimization is a reliability regression, it was done wrong. A bounds check is removed because something somewhere else is supposed to already guaratee it won't be violated, not just in a vacuum. If the guarantee stands, removing the extra check makes your program faster and there is no reliability regression whatsoever.

And how does performance improve reliability? Well, a more performant service is harder to overwhelm with a flood of requests.

[johnisgood]

"Removing an extra check", so there is a check, so the check is not removed?

[spiffyk]

It does not need to be an explicit check (i.e. a condition checking that your index is not out of bounds). You may structure your code in such a way that it becomes a mathematical impossibility to exceed the bounds. For a dumb trivial example, you have an array of 500 bytes and are accessing it with an 8-bit unsigned index - there's no explicit bounds check, but you can never exceed its bounds, because the index may only be 0-255.

Of course this is a very artificial and almost nonsensical example, but that is how you optimize bounds checks away - you just make it impossible for the bounds to be exceeded through means other than explicitly checking.

[mememememememo]

Somes directly like other commenters touch on. Less likely to saturate CPU quickly. Lower cost to run so can have more headroom.

But also the stuff you tend to do to make it fast makes it more reliable.

Local caches reduce network traffic. Memory is more reliable than network IO so it improves reliability.

Reducing lookup calls to other services (e.g. by supplying context earlier in the dependency chain) makes it faster and more reliable.

Your code will probably branch less and become more predictable too.

And often the code is simpler (sometimes not when a performance hack is used)

[cwaffles]

Less OOMs, less timeouts, less noisy neighbors problems affecting other apps