roh355/nanocache ? reverse-engineered prompt

Build me a small in memory cache server in C++ that speaks the Redis style protocol over a TCP connection. I want to be able to start it, connect with a simple client, and send basic commands like setting a key, getting a key, deleting a key, and maybe checking if a key exists. It should handle simple text requests and return proper responses so it feels like a lightweight cache service.

Please keep the code clean and easy to follow, with the cache logic separated from the network server and the request parsing. If it makes sense, add a simple snapshot or persistence step so the cache can be saved and restored. Make sure the server can deal with multiple commands in a row without crashing, and add a few examples or comments showing how to test it from the command line. If you need to check current protocol details online, go ahead and do that.