Scalability refers to a blockchain's ability to handle a growing number of transactions and users without sacrificing speed, cost, or decentralization. It's one of the biggest challenges facing blockchain technology.
The Scalability Problem
Bitcoin processes approximately 7 transactions per second (TPS). Ethereum handles about 15-30 TPS. Compare this to Visa's capacity of ~65,000 TPS. For blockchain to achieve mainstream adoption, it needs to scale dramatically.
Scaling Approaches
Layer 1 Scaling: Modifying the base blockchain itself — larger blocks, faster block times, sharding (splitting the chain into parallel segments).
Layer 2 Scaling: Building secondary protocols on top of the base chain — rollups, state channels, sidechains.
Alternative Architectures: New L1 chains designed for high throughput from the start (Solana, Sui, Aptos).
The Blockchain Trilemma
Coined by Vitalik Buterin, the trilemma states that a blockchain can only strongly achieve two of three properties: decentralization, security, and scalability. Different projects prioritize different tradeoffs.