The Scalability Trilemma (Bathtub Curve)
TL;DR
Bitcoin prioritizes decentralization and security over base-layer speed, scaling through layers rather than compromising its core properties.
What Is It?
The Scalability Trilemma suggests that a blockchain can only optimize for two of three major properties: Decentralization, Security, and Scalability (throughput).
- If you increase the block size (scaling), you increase the cost of running a node (centralization).
- If you decrease security (shorter block times), you increase the risk of double-spending or forks.
Why Does It Matter?
Bitcoin chooses to remain “slow” at the base layer to ensure that anyone with modest hardware can run a node. This makes the network resistant to capture and censorship. Scalability is achieved not by bloating the base layer, but by building fast, cheap layers (like Lightning) on top of it.
Analogy: The Bathtub Curve
Imagine a Bathtub:
- The Inlet: New data/transactions flowing in.
- The Outlet: The processing power/bandwidth of a single node.
- The Result: If you pump data in faster than the weakest node can drain (process) it, the system “overflows,” and nodes start falling out of sync, leading to centralisation (only “super-nodes” survive).