I never used D-lang in any production application.

But for an IOT prototype where the executable size and performance were very important we benchmarked D also along with Go and C#.NET Core.

I made the same prototype in Go, C#, Java(GraalVM Native Compile) and D-lang. The results were surprisingly positive for D-lang.

Best Peformance -> D-lang, next Go and then Java(GraalVM), C#.NET Core.

Executable Size -> D-lang:500kb, Go: 2.5 MB, C# : 11MB, Java(GraalVM):8MB.

Our major concern with D-lang was lack of dependable(tested) standard libraries.

Question: does D-lang use LLVM under the hood?

D has 3 main compiler implementations. One, LDC, is based on LLVM: https://github.com/ldc-developers/ldc

GDC is based on GCC: https://github.com/D-Programming-GDC/gdc

DMD is stand-alone: https://github.com/dlang/dmd