Why General-Purpose VMs Are Holding Back ZK-Rollups

EVM equivalence is a tax. The design goal of replicating Ethereum's execution environment forces ZK-Rollups to prove unnecessary computation, bloating proof generation times and costs. This architectural choice prioritizes developer convenience over optimal performance.

Specialized VMs unlock orders-of-magnitude gains. Projects like Starknet with Cairo and zkSync with its LLVM-based stack demonstrate that purpose-built VMs for ZK-proving achieve higher throughput and lower fees by eliminating redundant opcodes and state overhead.

The trade-off is ecosystem fragmentation. While Arbitrum and Optimism leverage EVM compatibility for rapid adoption, their long-term scaling is constrained. The industry must choose between short-term network effects and maximal technical efficiency.

General-purpose VMs prove waste. ZK-rollups like zkSync and Scroll must generate proofs for every EVM opcode in every transaction, even for simple transfers. This creates massive computational overhead because the prover's work scales with VM complexity, not user intent.

Flexibility creates proof bloat. A VM designed to handle arbitrary smart contracts, like the EVM or WASM, includes logic for edge cases rarely used in practice. Proving this unused speculative execution path is the primary cost driver, not the core state transition.

Application-specific VMs eliminate waste. Protocols like StarkWare's Cairo VM demonstrate that a domain-specific language tailored for proofs can be orders of magnitude more efficient. The prover only validates the logic the application actually uses.

Evidence: A zkEVM proving a simple ETH transfer requires verifying hundreds of opcodes. A purpose-built VM for a DEX like Uniswap V3 would prove only the constant product formula and fee logic, slashing prover costs by >90%.

General-purpose VMs are inefficient. ZK-Rollups like zkSync and Scroll prove every EVM opcode, forcing the prover to generate proofs for irrelevant logic like the gas metering system, bloating proof size and time.

ZK-unfriendly opcodes dominate cycles. Over 30% of execution traces in EVM-based rollups are for non-application logic like memory expansion and keccak256 hashing, which are computationally expensive to prove in ZK.

Application-specific VMs are the fix. StarkWare's Cairo VM and Polygon zkEVM's Type 2 approach demonstrate that designing VMs for ZK-proving from first principles reduces proof generation costs by orders of magnitude.

Evidence: A zkEVM proving a simple token transfer spends more cycles on the VM's internal bookkeeping than on the transfer logic itself, a fundamental architectural misalignment.

EVM compatibility fragments liquidity. Every new general-purpose ZK-rollup launches with an empty state, forcing protocols to deploy duplicate instances and users to bridge assets. This creates a liquidity cold start problem that monolithic chains like Solana or Sui avoid.

Developer attention becomes a zero-sum game. Teams must choose which of the 10+ EVM L2s to deploy on first, splitting community and engineering resources. This contrasts with app-specific rollups like dYdX v4 or Lyra, which capture 100% of their chain's throughput and fee revenue.

The tooling ecosystem is diluted. Infrastructure like The Graph, Pyth, or Gelato must maintain separate integrations and indexers for each L2, increasing overhead and delaying support. This slows the entire multi-chain ecosystem's iteration speed.

Evidence: Arbitrum and Optimism, after years, hold ~70% of all rollup TVL. New entrants like zkSync Era and Scroll struggle to attract sustainable liquidity beyond airdrop farming, demonstrating the winner-take-most dynamics in general-purpose environments.