API request: SeekForBase

Hello!

I'm looking for a way to find the longest key that matches a given prefix.
For example, given the keys:
```
1
12
123
```
If I look for `124` and there's no exact match, I'd like to get key `12` (the closest match with identical prefix -- not `1`).
This is useful when a tree is stored in rocksDB where each tree node is stored by its path down the tree, and I want to find the closest node in the tree for a given key.
The `SeekForPrev` API would return `123` in this example, so it's not a good fit.
Am I missing some API that supports this?
If not, could this feature be considered?

Thank you.