[Epic] choose and implement one underlying storage (prototype)

[jerryshao]

Describe the subtask

This issue is a follow-up issue of #48 , to implement one underlying storage for Graviton.

A simple candidate would be rocksdb, or we could choose FDB or other distributed storage for performance and fault tolerance.

Parent issue

#4

Task list

• [Subtask]Add KV backend storage interface for EntityStore #122
• [Subtask] Implement RocksDB backend storage for EntityStore  #121
• [Subtask] Implement key encoding of entity for key-value store #120

[jerryshao]

Hi @yuqi1129 , I'm going to assign this issue to you. You can separate to subtasks and track all the things here.

[yuqi1129]

@jerryshao got it