Again, not all key value are the same. TokyoCabinet isan old read-optimized btree based keyvalue engine. I don’t know about FoundationDB internals, but you might want write optimized LSM based db for your use-case.
More importantly it does not look like a good idea to rely on dead unmaintained technology with no commit in the past few years to store your data while you can just use techs everyone else is using and debugging like rocksdb based distributed kv store or foundationdb