Recently, I'm doing some research in data storage with blockchain, ONLY for data that's very small like a public key or a hash or a self-defined field.
I already knew how to use Bitcoin system publishing my data which is through OP_RETURN instruction in tx_out.
HOWEVER, there are a question I don't know how to resolve.
The OP_RETURN in tx_out CAN NOT contain much data length once time, so far as I knew the max length of data payload of OP_RETURN is 80 bytes. Is there a different Blockchain system that supports small data storage well and maybe without transaction fee?
There are tons of bitcoin forks that also use OP_RETURN the same way with larger sizes, such as bitcoin cash. In addition to that, all smart contract platforms can do the same and store data. Just write a function that returns a fixed string in your smart contract and put the data there.
If you feel the need to ask for follow up questions, just know that you're asking this question in the wrong place. This is a programming forum, not enthusiast forum. You're better off asking this in places like reddit/cryptocurrency or similar.