Scalability

In practice, scalability is measured in how many transactions a network can confirm per second (its throughput) and how that number behaves as demand grows. A base-layer blockchain that must have every node re-execute every transaction naturally caps out: Bitcoin settles roughly 7 transactions per second and unmodified Ethereum around 15 to 30, far below the thousands per second that centralized payment networks handle. That ceiling is what makes scalability a design problem rather than a simple hardware upgrade.

Engineers have pursued two broad routes around it. The first moves activity off the base chain: Layer 2 rollups batch thousands of transactions, execute them elsewhere, and post a compressed proof back to the main chain, inheriting its security while multiplying capacity. Ethereum's 2024 Dencun upgrade added dedicated "blob" data space for exactly this purpose, and rollups such as Arbitrum, Optimism, and Base now carry the large majority of Ethereum-related activity. The second route redesigns the base layer itself, through sharding (splitting validation work across subsets of nodes), larger blocks, or faster consensus mechanisms, as seen on chains like Solana that process transactions in parallel.

Every approach involves trade-offs. Higher throughput often concentrates transaction ordering in a small number of sequencers or validators, weakening decentralization, or requires nodes with more powerful hardware, narrowing who can participate. This tension is commonly described as the blockchain trilemma: scalability, security, and decentralization are difficult to maximize simultaneously, and most networks knowingly prioritize two.