Comment by Mark on "Why do startups use languages like Python and Ruby which are slow but big companies use Go, Java or even Scala for their backend?"

The main reason is that languages like Python are higher-level and require less boilerplate (e.g. types). Startup success often depends on being first, so this is essential.

But note that statically typed languages like Java are not just faster (although that's part of it). They're also easier to scale. When more developers join and the codebase grows, most of the time you'll be changing code you're much less familiar with than you are with your personal projects. Static types help because:

Types give useful context, which you don't need if you wrote the code yourself recently, but do if you're seeing it for the first time. It's like required documentation that doesn't get outdated.
Types help catch mistakes at compile time. Larger projects are also harder to fully test (because they have more functionality and execution paths), so catching things at compile time becomes more beneficial.
As you said, static typing helps the compiler make code faster.

(Java is not the best example since it's type system isn't great. There are other languages that have much more expressive type systems, so they catch many more errors at compile time).

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