Life of a Transaction

That waiting room you just walked through is real, and it has a name. The pool of signed transactions that have been broadcast but not yet sealed into a batch is called the mempool.

Hold on to one fact about it: the mempool is public. While your letter waits, anyone watching can read it. That is normal and not, by itself, dangerous, but it is the reason a later checkpoint exists at all.

Each sealed batch has limited room. On a busy day there are far more letters waiting than seats in the next batch, so they cannot all go at once. The post office does not pick by who arrived first. It picks by who attached the most postage.

That postage has a name: gas. It is the fee you pay for room in a batch. When the city is quiet, a seat is cheap because few letters compete. When everyone is sending at once, they bid against each other and the price of a seat climbs. Same letter, same distance, the cost swings with how busy the office is.

You send the same amount to the same friend two days running. Yesterday the fee was a few cents. Today the wallet wants several dollars for the identical action.

Your letter did not change. So what did?

Once your letter is picked up and sealed into a batch, it has happened, but it is not yet set in stone. Each new batch stacked on top of yours is one confirmation. These are the same sealing locks you saw in the ledger checkpoint, doing their job in real time.

One layer means it is in. Several layers mean rewriting history would cost an attacker more than it could ever be worth, which is what we mean by final. The deeper your letter sits under newer batches, the more settled it is.

Remember the cheaper floors you saw on the city map. This is the reason they were built. When postage on the ground floor climbed, people wanted a way to send without paying for a full seat every time.

The cheap floors do it by sharing. They gather thousands of letters, bundle them, and post a single compact receipt down to the expensive ground floor. Everyone in the bundle splits one postage bill, so each letter costs a fraction. We open up exactly how that bundling works in a later checkpoint.

Because every letter is public, there is a window for reading them: a block explorer, the best known being Etherscan. It is plain-text proof of what happened, open to anyone, and almost nobody teaches you to read it.

It is simpler than it looks. Five rows carry the whole story: who sent it, where it went, how much, what postage they paid, and whether it is still waiting or already sealed. Learn these five and you can check any transaction yourself instead of trusting a screenshot.

You sent something an hour ago and the wallet still says pending. Nothing is moving. The first instinct is panic: the money has vanished into the machine.

Before you panic, reason with the model you just built. Your letter is sitting in the public waiting room, and you can picture exactly why it has not been picked up yet.

You have learned that more confirmation layers mean more settled. A careful friend takes the obvious next step: always wait for a long stack of confirmations before you trust that anything went through.

It sounds safe, and like most blanket rules it is wrong at the edges. So pressure-test it before you adopt it.

You followed one letter the whole way: signed with your key, announced to everyone, waiting in a public room, sealed into a batch, buried under layers until undoing it would cost more than it could ever pay.

But look again at the to field on the explorer. Some addresses are not people at all. They are programs, holding money and following rules with no one behind them.

Next: what actually lives at a contract address. Smart contracts, under the hood.