Let’s look at serious scientific and high performance production grade software
C++
tensors + grad PyTorchC++
tensors + grad TensorFlowC
tensors numpyC++
random forests XGBoostC++
computer vision OpenCVC++
statistics, MCMC StanFortran/C/R
math RC/C++/Julia
math JuliaMatlab/Java/C/C++
math MatlabC
CPython, default Python interpreterC++
molecular simulation GromacsC++
solid engineering simulation and 3D modeling Solidworks, AutocadC
video processing ffmpegC++
video processing gstreamerC++
audio processing google/mediapipeC++
GPU parallel algorithms CUDAC++
game engines (physics simulation, business logic, networking) Unity, Unreal EnigneC++
web servers Erlang VM, Node.JS/V8, HHVMC++
Google data warehouse (GFS, BigTable, MapReduce)Java/Scala
open source data warehouse (HDFS, Hadoop, Kafka, Spark)C
databases PostgreSQL, Redis, MemcachedC++
databases MySQLGo
time series database InfluxDB, they considered C/C++ thoughC
productivity tools MS Excel, Google Chrome, Firefox, PhotoshopC
geo algorithms uber/h3C++
geo algorithms google/s2C++
original Google MapsUPD: 2020-06-08
UPD: 2020-12-29
C++
Zoom is running C++ servers for their video pipelineC++ is leading by a large margin. Its ecosystem is astonishing. Pretty much everything of significance has been written and maintained in C++. Bare in mind, other languages like Golang or Rust have been around for around 10 years, still main applications did not migrate to them. Even more, TensorFlow itself is not in Golang, even though they are both from Google and Tensorflow created 6 years later. It is true that Golang is having momentum in service development — things like networking, ORM, business logic — yet it is used in not much anything else.
Some languages was made by mistake (Javascript), some languages are too minimal (Golang), some are not scalable (Python). Maybe, then C++ has plenty of good besides performance? It has first class OOP, generics, operator overloading, standard library, gRPC and Apache Thirft, with RAII memory leaks are rare. Where I am going with this? If you are going to write high performance software likely it is going to be in C++.