The Blockchain Scalability Problem

What you'll learn

• The Scalability Trilemma
• TPS in Context: 7, 30, and 65,000
• What Happens During Network Congestion
• Why Bigger Blocks Are Not the Answer
• Layer 2: Scaling Without Rebuilding the Base

Key terms

Scalability trilemma

The principle that a single blockchain layer can optimize for at most two of decentralization, security, and scalability. Achieving all three requires a multi-layer architecture.

Transactions per second (TPS)

A throughput measure. Bitcoin handles approximately 7 TPS, Ethereum 15 to 30 TPS, Visa around 1,700 average and 65,000 peak, PayPal 193 TPS.

Mempool

The unconfirmed-transaction memory pool maintained by every Ethereum node. Transactions wait here until included in a block; during congestion, the mempool grows large and low-fee transactions wait or expire.

EIP-1559

The Ethereum fee-market upgrade that introduced a protocol-set base fee plus a user-chosen priority tip, replacing the previous first-price auction. The base fee is burned, reducing ETH supply.

Block Size Wars

The 2015-2017 Bitcoin community dispute over raising the 1 MB block size limit. Resolution: Bitcoin retained small blocks plus SegWit; Bitcoin Cash forked off with larger blocks in August 2017.

L2BEAT

The leading site for tracking Layer 2 metrics. Recorded peak total value secured of approximately 49 billion dollars in October 2025; about 38 billion dollars in December 2025.

Gas limit

A parameter analogous to block size for Ethereum. Has risen from approximately 3 million in 2015 to around 36 million in 2025 through gradual, deliberate increases.

Rollup-centric roadmap

Ethereum's 2020+ scaling strategy as articulated by Vitalik Buterin: keep the base layer slow and secure; scale execution through rollups anchored to it. The dominant Ethereum scaling philosophy today.