There is an open-source project by LMAX (a forex trading company) called Disruptor[1] that squeezes as much as possible out of the JVM. It's awesome. I ported it to C++ years ago when I wanted to learn about low-latency techniques. However, if you look at the code they need to actually break out of the JVM's safety net to get the performance they need[2]. I couldn't help but ask myself why they didn't just use C++, and when asked one of the devs did admit that their own C++ ports had an approx 10% performance increase (although this was ~7 years ago maybe)
Rust is certainly interesting and it's on my radar. I wonder though, when it comes to having it in use in anger if its guarantees turn out to be over sold, just like the JVM's safety claims were. Time will tell.
Edit: I tend to focus on comapring against the JVM because pretty much any framework you use on The Cloud is JVM based. I'm of the opinion that there are cost savings to be had if these were ported to more appropriate languages, hence the Cassandra vs Scylla comparison. The money saved was 'noticeable'.
Which is why such projects use the JVM, they save money in developer salaries, developer pool, bug fixes due to security exploits, available set of tooling and libraries, while caring to hand optimize a tiny set of libraries for specialized use cases.
Java 15 just accepted the JEP for native memory management, yet another stepping stone for having value types support.
If the cadence continues, Java will eventually have all the features that it should have had in 1996, had Sun properly taken into consideration languages like Modula-3 and Eiffel.
Which you can get today in a language like Swift, C#, Nim or D, productivity of GC, type safe, while having the language features to do C++ like resource management.
Rust is certainly interesting and it's on my radar. I wonder though, when it comes to having it in use in anger if its guarantees turn out to be over sold, just like the JVM's safety claims were. Time will tell.
Edit: I tend to focus on comapring against the JVM because pretty much any framework you use on The Cloud is JVM based. I'm of the opinion that there are cost savings to be had if these were ported to more appropriate languages, hence the Cassandra vs Scylla comparison. The money saved was 'noticeable'.
[1] https://github.com/LMAX-Exchange/disruptor [2] http://mishadoff.com/blog/java-magic-part-4-sun-dot-misc-dot...