As a reader, I strong dislike prologues. They rarely tell me anything that hinting at backstory doesn't tell me.
As a writer, I write a lot of backstory. Most of this is never put into my story.
Currently, I'm writing an urban fantasy. Our protagonist is a skilled martial artist. 1) He studied martial arts for many years. 2) He is an active member of the local chapter of a medievalist society. 3) He also seems to be a berserk. He is also living with his two girlfriends (a recent change in his life).
I spent time trying to figure out how to shoehorn all this into the very beginning of the story, and nothing was working until I just dropped him into the middle of a fight. This brings him to the attention of the protagonist which will result in the inciting incident.
The back story is now naturally unfolding, with very small bits dropped to the reader every now and then.
I have a history of the characters, in a general way, from the time before they were born (yes, the three main characters mothers knew each other). Most of this history will never be made public. A small amount might be. However, most of it really doesn't matter to the story, and shouldn't take any more space than it needs to to add some flavor.
For example, Mariko's mother is a Kitsune; this is somewhat important to the story. On the other hand, why her mother stays with her father is somewhat of a mystery. That she was the one that instigated the thruple of the three main characters is unknown to the characters and the readers (Mariko might suspect something, but if so she hasn't told anybody else). And unless I find a good reason, it will remain that way. If readers ask for more backstory, then I can write some of it in a short story. Think of that as job security. :)
The way I'm doing this is one way to handle this. I'm doing it this way because I feel the story I'm telling is more important than the history of the characters.