MD5

generacodice.com/en/articolo/175462/sales-y-contraseñas—prefijo-o-de-sufijo unlike what others said, it does matter! and as @einstein if you care use HMAC.

why prefix is bad, because one can calculate the intermediate state of the checksum up to the given fixed salt prefix. then start calculating the rest in parallel. In summary phrase+salt is more secure than salt+phrase, but HMAC(salt, phrase) is even better.

!! https://www.skullsecurity.org/2012/everything-you-need-to-know-about-hash-length-extension-attacks

https://crypto.stackexchange.com/questions/1632/does-the-position-of-the-salt-improve-its-effectiveness-when-hashing

https://blog.silentsignal.eu/2015/09/17/finding-the-salt-with-sql-inception/

https://www.researchgate.net/publication/266650299_Security_Analysis_of_MD5_Algorithm_in_Password_Storage

https://ieeexplore.ieee.org/document/6516321

https://security.stackexchange.com/questions/211478/does-putting-salt-first-make-it-easier-for-attacker-to-bruteforce-the-hash