I learned that the blocks and transactions are stored locally in .bitcoin/blocks/index and .bitcoin/chainstate databases, respectively. I want to make a direct query to those databases to measure the response time. However, I found it hard to understand the format and the best way to access to the data. I am using Plyvel, but I couldn't formulate the exact query, for example to search for a particular transaction identified by its hash value, or searching for the all transactions made by a particular sender identified by the hash of its public address.
Any help, please.