Arc 3 of 100 Days of Solana was the arc where Solana stopped being something we read from and started being something we wrote to .

Across the arc, we inspected transactions, sent SOL on devnet, built a transfer tool, tracked confirmation, and deliberately triggered failures. That shift changes how everything else fits together: accounts, programs, fees, confirmation, errors, and application state.

They all hang off one idea:

A Solana transaction is a signed request to change on-chain state.

Reading is pretty much like Web2. Writing is not.

Reading from Solana maps neatly onto things most Web2 developers already do. You ask for a balance. You fetch account data. You look up a transaction. The network answers.

Writing is different. It is closer to making a POST request that changes production data, except there is no single server receiving it.

In a Web2 app, a write usually follows a familiar path: take some input, check authorization, run logic, change state, return a result.…