Created by: dzhwinter

Do we need a DB to saving and read checkpoint? For the checkpoint feature, we need to write it periodically and replace the old checkpoint.
with a DB: pros:

• do not need to read/write fs, speed up read/write
• save parameter and training state base key immediately, do not need any manually replace old file operation.

cons:

• more dependencies, consume resources in backend.
• need to write convert tool if we need the checkpoint file.

here DB refer to key-value database, e.g. rocksdb, leveldb