Why the type of object key is not properly picked by typescript?

const k: Record<'a' | 'b', number> = { a: 5, b: 6 };

Object.entries(k).forEach(([key, value]) => {
  // key: string
  // value: number
});

I was expecting the types to be

key: 'a' | 'b'
value: number

Because we are saying Record<'a' | 'b', number> and not Record<string, number>.

Also how can I fix this in a safe way with out using any?

playground

There is a possible duplicate here. But that question is not following the minimal-reproducible-example - and hence the answers are too. I felt like that thread is taking too much energy to understand because it is not generalized.