C and C++ are dangerous languages filled with security failings and footguns, and no modern app should be written in them.
It's been my experience that well-written low-level Java code runs at about 75% the speed of good C code. (Of course lazy coders write in cushy Java which is much slower). When written efficiently, Java's biggest slowdown lies in array access (C and C++ array access is fast because it is very, very unsafe). But Java makes up for this in having a GC which will coalesce related objects into the same page and so take advantage of cache coherency effects in ways malloc and free cannot possibly do. I have some allocation-heavy algorithms in Java which are, as a result, significantly faster than well-written equivalents in C.
I've done a lot of performance engineering in both C++ and Java. Every optimization available in Java also exists in C++ but the reverse is not true, which is why C++ is always faster. Every example I have ever seen of Java being faster than C++ was just poorly optimized code. The heuristic I use is that heavily optimized C++ is about twice as fast as heavily optimized Java at the limit. And this requires some non-idiomatic and ugly Java that isn't nice to maintain.
This doesn't necessarily make Java the wrong choice though. Few organizations prioritize absolute performance above all other things. There are practical tradeoffs.
@pron, who works on the JVM and is a C++ expert, has been writing a lot recently about low level languages becoming increasingly impossible to optimize with more LOC and more people working on it (dozens, or even hundreds of developers).
The idea being be a language with an aggressive JIT, moving garbage collector, and bump allocation is going to allocate/deallocte faster than malloc, and get the most important average optimizations at all times, where as the equivalent low level app will struggle to get the ideal allocation pattern the more people that work on it, or be forced to use slow dynamic dispatch. He wouldn't describe a GC as pessimistic, he'd say it's literally faster, and that's why he (a C++ programmer) works on it. The JVM was built by people saying "we are doing a handful of the same things in C++ all the time."
There are specific cases where it's good to have low level control, but they aren't everywhere.
May be true between late 90s to late mid 10s. Both Java and JVM has had enormous of work going into it. 2026 the JVM is pretty damn good pieces of engineering.
C++ or go? Then you'll have to take a very closer look, because the java JIT is wonderful. A masterpiece of several hands, actually.
Of course we are talking generals here. Sometimes the above is acceptable and Java/JIT is just fine. Sometimes it is unacceptable and you cannot use Java/JIT. Know your domain.
Of course in all cases (C, Rust, C++), you have to understand the system and what it is doing. Every language has a standard library that will do things that are not low latency on you. You have to know which library functions will do what, memory allocation and copies are both things that code often does without thought that are incompatible with low latency. No matter what you need to know what your language does that is against you.
To avoid the compilation etc. hit, common practice is to do some "warmups" before serving users. (Another reply has other ways to avoid this hit.)
Handling exceptions is higher latency, but they can/should be optimized out, so you're not hitting exceptions as part of your standard workflow (or even your 1% workflow).
There's startup "AOT cache" via Leyden that speeds up startup. Isn't native speed up it's quite a big boost.
Then there's GraalVM that does give you a native image. Real AOT.
Not true. Many benchmarks have shown otherwise. it is at least competitive in many areas.
> and the former will also be way way more easy to run, troubleshoot, interpret logs from
No language will save you from poor logging practices. If you log every debug log it's not Java's problem. No 1 says you have to log the full stack trace if that's your concern. You can configure / strip / do anything. Learn to use the stack.
Everyone that has a minimal experience with these knows it is not true.
While performance ceiling is likely higher in C/C++/Rust (but not Go), when we move beyond microbenchmarks Java provides competitive performance with much better ergonomics. Not to mention strictly superior tooling.
Am I the only one who thinks "pebkac" is a self-own? If you're blaming your users for the tool, it feels like maybe your tool is just hard to use properly. I have no doubt that there are big, fast, low latency Java systems out there, but why does it take so much extra effort to build these systems in Java compared with other languages? Maybe it would be better to have competent developers focus their attention beyond managing Java's shortcomings?
I'm not even hating on Java here--I actually like the JVM quite a bit, but blaming users feels like an implicit admission.
There's no such thing as a programming language that guarantees excellent performance regardless of programming competence.
> why does it take so much extra effort to build these systems in Java compared with other languages?
They didn't say that.
The entire premise of the conversation is that other languages allow us to write idiomatic code and get good performance, and the parent's position was that Java requires "competent developers". So yes, the parent did say that, however...
> There's no such thing as a programming language that guarantees excellent performance regardless of programming competence.
No one made any claim remotely like this. This is a very obvious straw man argument. What was argued was that you can get decent performance from other languages without additional competence beyond idiomatic code.