Other than the choice problem of deciding what language to build new features in (which needs a clear policy), I don’t see why maintaining a mixed language codebase HAS to be terrible.
In my current job, also at FAANG, my team (albeit SRE team, not dev team), owns moderately sized codebases in C++, Go, Python and a small amount of Java. There are people “specialised” in each language, but also everyone is generally competent enough to at least read and vaguely understand code in other languages.
Now of course sometimes the issue is in the special semantics of the language and you need someone specialised to deal with it, but there’s also a large percentage which is logic problems that anyone should be able to spot, or minor changes which anyone can make.
The key problem in the situation you described seems to be the dysfunction in the teams about arguing for THEIR side, vs viewing the choice of language as any other technical decision that should be made with the bigger picture in mind. I think this partly stems from unclear leadership of how to evaluate the decision. Ideally you’d have guidance on which to prioritise between rapid development and consistency to guide your decisions and make your language choice based on that.
As your codebase scales beyond a certain point, siloing is pretty inevitable and it is better to focus on building a tree of systems and who is responsible for what. However that doesn’t absolve especially the leads from ONLY caring about their own system. Someone needs to understand things approximately to at least isolate problems between various connected systems, even if they don’t specialise in all of them.
In my current job, also at FAANG, my team (albeit SRE team, not dev team), owns moderately sized codebases in C++, Go, Python and a small amount of Java. There are people “specialised” in each language, but also everyone is generally competent enough to at least read and vaguely understand code in other languages.
Now of course sometimes the issue is in the special semantics of the language and you need someone specialised to deal with it, but there’s also a large percentage which is logic problems that anyone should be able to spot, or minor changes which anyone can make.
The key problem in the situation you described seems to be the dysfunction in the teams about arguing for THEIR side, vs viewing the choice of language as any other technical decision that should be made with the bigger picture in mind. I think this partly stems from unclear leadership of how to evaluate the decision. Ideally you’d have guidance on which to prioritise between rapid development and consistency to guide your decisions and make your language choice based on that.
As your codebase scales beyond a certain point, siloing is pretty inevitable and it is better to focus on building a tree of systems and who is responsible for what. However that doesn’t absolve especially the leads from ONLY caring about their own system. Someone needs to understand things approximately to at least isolate problems between various connected systems, even if they don’t specialise in all of them.