What Is a Cryptocurrency
Every blockchain is a compromise. The only question is which one.
Decentralisation, security, scalability. All three are worth wanting, and a network can rarely maximise all three at once — which is why "faster" is a question, not an answer.
The problem
Take one corner to the maximum.
Three goals, one budget. Push a corner as far as it goes and read what the other two hand over.
Three goals on one budget
BUDGET 240/240Many independent participants can check the rules and run the network themselves.
Resistance to attacks and to manipulation of the record.
Low fees and fast confirmation, for payments, gaming, DeFi and global apps.
All three sit level. Press a corner to push it as far as the budget allows.
Illustrative model — the source describes the mechanism, not these figures. No real network's throughput is being claimed here.
None of the three is a bad goal. Decentralisation buys independence, security buys robustness, scalability buys usability — you want all of them. The tension appears the moment you try to maximise all three at once, because each one is paid for out of something the others need. Every blockchain that exists has already made this choice: some deliberately and robustly, some carelessly. Which is why the useful question about a network is never "how fast is it?" but what does the speed cost, and who pays for it?
The definition
Three things the trilemma is not.
Tap each card for what it actually says.
Hands on
Which goal does the statement serve?
Three properties, all desirable. Pick one and see the two statements that belong to it.
Decentralisation
FOR INDEPENDENCEEvery one of these statements is something you would want. That is exactly why they collide.
The bridge
Bitcoin's answer, and the work in progress.
A trade-off is not a ceiling. It is a design problem people are still working on.
That is the tool you take out of this lesson. Not a ranking of networks — the trilemma never gives you one — but a question you can ask about any of them: what does the speed cost, and who pays for it? The next lesson runs the same kind of comparison against something far older than any blockchain: gold.
Check yourself
Five questions.
Answers come straight from this lesson. Submitting completes it.