Blockchain Trilemma

The blockchain trilemma is the observation, popularised by Vitalik Buterin, that a blockchain struggles to maximise decentralisation, security and scalability at the same time; pushing hard on one typically costs one of the others. Raising throughput by demanding powerful, expensive nodes shrinks the number of people who can validate, which weakens decentralisation. Shrinking the validator set to reach faster consensus concentrates the power to censor or reorder transactions. Much of modern protocol design is an attempt to soften the trade-off rather than escape it: rollups move execution off the base layer, while sharding and data-availability sampling let light nodes verify without storing everything. The trilemma is a design heuristic, not a proven law, and it is most useful for asking what a chain gave up.