Blockchain trilemma

The blockchain trilemma, a phrase popularised by Ethereum co-founder Vitalik Buterin, is the idea that a blockchain struggles to achieve three goals at once: decentralisation, security and scalability. Improving one usually means compromising on another.

For example, a chain can process more transactions by using bigger blocks or fewer, more powerful validators, but that raises the cost of running a node and concentrates control. A chain can be very decentralised and secure, as Bitcoin aims to be, but then it can handle only a limited number of transactions on the base layer.

Different projects choose different balances. Bitcoin and Ethereum prioritise decentralisation and security and scale through layer 2 networks. High-throughput chains such as Solana require more powerful hardware to run a validator in exchange for speed. Techniques like rollups, sharding and zero-knowledge proofs are attempts to ease the trade-off. The trilemma is a useful rule of thumb rather than a mathematical law.