Unit 2 · Level 2 · The scaling problem
Block space is scarce
In December 2017, a game called CryptoKitties (collectible digital cats you breed on-chain) went viral and at its peak accounted for over 10% of all Ethereum traffic. Tens of thousands of transactions jammed the queue, and fees for everyone spiked. It happened again in the 2021 NFT boom, when hot mints pushed a single swap above €100 in gas. Block space is scarce, and when demand surges, you feel it in your wallet.
Free to play. No ads, no token, no account needed to start.
What you get asked
How does a blockchain decide whose transaction gets into the next block?
Block space is a fee market, an auction. Quiet days are cheap; the moment something goes viral, the bidding war begins.
A chain fits about 120 simple transfers per block and produces one block every 12 seconds. Roughly how many transfers per second is that?
120 ÷ 12 = 10 per second, for the whole world. Card networks handle thousands per second, which is exactly why scaling became crypto's obsession.
In December 2017, what famously clogged Ethereum for days?
CryptoKitties. One popular app was enough to congest the entire world computer. A very cute, very expensive stress test.
Put the congestion spiral in order
Note who pays the price: not just the app's fans, but everyone sharing the chain. Congestion is a tax on all your neighbours.
When demand for block space exceeds supply, transaction ___ rise.
Scarce supply plus surging demand equals higher prices: the same economics as concert tickets, just measured in gwei. 🐜
The rest of this unit
Why block space is scarce, and why 'just make blocks bigger' started a war.