As far as I know, in order to estimate a fee of a Tezos transaction, a following method needs to be called on a Tezos node:
../<block_id>/helpers/scripts/run_operation . At least this is how it's implemented in ConseilJS and that's what I found in documentation.
One of the parameters of that method is a transaction signature that obviously requires using a private key.
My question is: is it possible to estimate fee without using a private key? I would imagine it should be, since that's also possible in other blockchains - eg. Ethereum.
Please do note that I am interested in a solution that can be applied in a nodejs app, so a CLI method (if such exists) is not enough.