Thanks, it is really helpful.
One final note which I wanted to ask.
The DB - is this a file or a DB? If so, what are the underlying modules and schema can you point out?
Meetreks
What DB? Bitcoin Core uses two databases, Berkeley DB and Level DB. The Berkeley DB file is the wallet file. Or is used in the wallet for sitting you private keys. The level DB is for storing the blockchain. It contains an index of blocks and transactions.