ZK Rollups like zkSync Era and StarkNet require immediate, verifiable data availability (DA) for their validity proofs. Their security is mathematically guaranteed upon proof verification, which depends on having the transaction data to reconstruct state. This allows them to leverage alternative DA layers like Celestia or EigenDA for significant cost savings—often reducing DA costs by 90%+ compared to Ethereum mainnet—without compromising finality. The data is needed only long enough for the proof to be verified and challenged, enabling more aggressive DA optimization.
LABS
Comparisons
DA for ZK Rollups vs DA for Optimistic Rollups
A technical analysis of how the core security mechanisms of ZK and Optimistic Rollups fundamentally shape their data availability requirements, cost structures, and trust assumptions for CTOs and protocol architects.
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introduction
THE ANALYSIS
Introduction: The Core Proof Mechanism Dictates DA Strategy
The fundamental security model of your rollup—ZK or Optimistic—directly determines the cost, latency, and security trade-offs of your data availability solution.
Optimistic Rollups such as Arbitrum and Optimism have a fundamentally different security requirement: a long challenge period (typically 7 days) where transaction data must be available for fraud proofs. This extended window mandates highly secure, persistent DA, making Ethereum's calldata a preferred, albeit expensive, choice. While solutions like EIP-4844 proto-danksharding (blobs) reduce costs, the core model prioritizes censorship resistance and data permanence over pure cost minimization, as the system must assume data can be withheld by a malicious party.
The architectural divergence creates a clear trade-off: ZK Rollups can aggressively pursue cost-efficient external DA for applications prioritizing low transaction fees and fast finality. Optimistic Rollups are architecturally tied to highly available, persistent DA layers, making them a robust choice for protocols where maximum security and Ethereum-aligned guarantees are paramount, even at a higher operational cost.
tldr-summary
ZK Rollup DA vs Optimistic Rollup DA
TL;DR: Key Differentiators at a Glance
A data-driven comparison of Data Availability (DA) trade-offs for the two dominant scaling paradigms. The core tension is between cryptographic certainty and economic efficiency.
01
ZK Rollup DA: Cryptographic Security
Finality at Layer 1: State transitions are verified by validity proofs (ZK-SNARKs/STARKs) before data is posted. This means the DA layer only needs to store data for a short, fixed period (e.g., ~1 day for proofs to be generated and verified). This enables highly secure external DA solutions like Celestia, Avail, or EigenDA, as the security assumption is purely data availability, not long-term fraud detection.
Best for: Protocols requiring maximum security and capital efficiency (e.g., DeFi, bridges) where instant finality reduces liquidity lock-up times.
02
ZK Rollup DA: Cost Efficiency
Lower Long-Term Data Burden: Because validity proofs guarantee correctness, historical data is needed primarily for node synchronization, not for dispute resolution. This allows for aggressive data pruning and lower persistent storage costs on the DA layer. Rollups like zkSync and StarkNet leverage this for cheaper overall transaction fees.
Key Metric: Projects like Polygon zkEVM using Celestia target sub-$0.01 DA costs per transaction, a major component of total fee reduction.
03
Optimistic Rollup DA: Economic Simplicity
Relies on Fraud Proofs: Transactions are assumed valid but can be challenged during a long challenge window (typically 7 days). This requires all transaction data to be available on-chain for the entire window for any verifier to reconstruct state and submit a proof. This strongly incentivizes using the native L1 (Ethereum) for DA, as its high security is needed to underpin the economic game.
Best for: General-purpose rollups (e.g., Optimism, Base) prioritizing maximum compatibility with Ethereum's security model and tooling, accepting higher baseline costs.
04
Optimistic Rollup DA: Higher Baseline Cost & Latency
Mandatory L1 Data Posting: Every transaction's calldata must be published to Ethereum mainnet to enable fraud proofs, leading to consistently higher DA fees driven by Ethereum gas prices. This is the primary cost bottleneck for chains like Arbitrum.
Withdrawal Delay: The 7-day challenge period creates a fundamental latency for cross-chain asset withdrawals, requiring liquidity providers or bridging protocols to mitigate. This impacts user experience and capital efficiency for frequent movers.
ZK ROLLUPS VS OPTIMISTIC ROLLUPS
Data Availability Feature Comparison
Direct comparison of key data availability mechanisms, costs, and security models for rollup architectures.
| Metric | ZK Rollups (e.g., zkSync, StarkNet) | Optimistic Rollups (e.g., Arbitrum, Optimism) |
|---|---|---|
DA Cost per MB (On Ethereum) | $800 - $1,200 | $800 - $1,200 |
Time to Finality (With Proof) | ~10 minutes | ~7 days |
DA Security Assumption | Cryptographic Validity Proofs | Economic & Fraud Proofs |
Off-Chain DA Layer Support | ||
EIP-4844 Blob Fee Savings | ~90% | ~90% |
Primary DA Layer | Ethereum L1 | Ethereum L1 |
Data Compression Efficiency | ~10-100x | ~10-100x |
pros-cons-a
DA for ZK Rollups vs DA for Optimistic Rollups
ZK Rollup Data Availability: Pros and Cons
Key architectural trade-offs and performance implications for protocol architects.
01
ZK Rollup DA: Security & Finality
State validity is guaranteed by cryptographic proofs, not social consensus. This allows for secure data availability (DA) on alternative layers like Celestia, Avail, or EigenDA without compromising security. Finality is achieved in minutes (e.g., zkSync Era ~1 hour, StarkNet ~3-6 hours) vs. the 7-day window for Optimistic Rollups. This matters for exchanges and high-value DeFi needing faster capital efficiency.
02
ZK Rollup DA: Cost Efficiency
Lower long-term DA costs are possible by posting only state diffs and validity proofs, not full transaction data. Protocols like StarkNet and zkSync can batch proofs for thousands of transactions, amortizing L1 calldata costs. This enables scalable micro-transactions and gaming where fee predictability is critical. However, initial proving costs (prover hardware) are higher.
03
Optimistic Rollup DA: Simplicity & Composability
Full transaction data on L1 (Ethereum) ensures maximum security and seamless trust-minimized bridging. The 7-day challenge period, while slow, allows for simple fraud proofs and maintains strong cross-rollup composability via shared L1 settlement (e.g., Arbitrum and Optimism's Cannon fraud proof system). This matters for protocols prioritizing Ethereum-level security and existing tooling compatibility.
04
Optimistic Rollup DA: Ecosystem Maturity
Larger TVL and established tooling (Arbitrum: $18B+, Optimism: $7B+ TVL) benefit from the straightforward DA model. The requirement to post all data to Ethereum has fostered robust infrastructure like The Graph for indexing and block explorers. This matters for enterprise deployments and large-scale DeFi where network effects and developer familiarity reduce integration risk.
pros-cons-b
ZK ROLLUP DA VS. OPTIMISTIC ROLLUP DA
Optimistic Rollup Data Availability: Pros and Cons
Key architectural trade-offs in data availability strategies, focusing on cost, security, and finality.
01
ZK Rollup DA: Cost & Finality
Lower On-Chain Costs: ZK-Rollups like StarkNet and zkSync publish succinct validity proofs, not full transaction data, leading to ~80% lower L1 calldata costs. Instant Finality: State updates are final upon proof verification (~10-20 min), enabling fast withdrawals and CEX integration. This matters for high-frequency DeFi and applications requiring strong capital efficiency.
02
ZK Rollup DA: Security & Complexity
Cryptographic Security: Validity proofs (ZK-SNARKs/STARKs) guarantee correctness, removing the need for a fraud-proof window. High Setup Complexity: Requires trusted setups for SNARKs or complex proving systems (STARKs). This matters for protocols where absolute state integrity is non-negotiable, but it demands specialized cryptographic expertise.
03
Optimistic Rollup DA: Cost & Ecosystem
Higher Baseline Costs: Optimistic Rollups like Arbitrum and Optimism must post all transaction data to L1, incurring higher calldata fees. Mature Tooling & EVM Equivalence: Full data availability enables seamless compatibility with Ethereum tooling (MetaMask, Hardhat). This matters for teams prioritizing developer experience and rapid deployment over minimal transaction costs.
04
Optimistic Rollup DA: Security & Latency
Economic Security with Delay: Relies on a 7-day fraud-proof challenge window, introducing a significant withdrawal delay. Censorship Resistance: Full data on-chain allows anyone to reconstruct state and submit fraud proofs. This matters for applications where maximum decentralization and battle-tested security are prioritized, and users can tolerate week-long exit periods.
ZK VS. OPTIMISTIC ROLLUPS
Technical Deep Dive: How Proofs Shape DA Requirements
The fundamental difference between ZK and Optimistic rollups—their proof mechanism—creates vastly different requirements for data availability. This analysis breaks down the technical trade-offs in security, cost, and performance.
ZK Rollups require significantly less on-chain data availability than Optimistic Rollups. A ZK validity proof (e.g., a STARK or SNARK) compresses thousands of transactions into a single, small proof, requiring only state diffs to be posted. In contrast, Optimistic Rollups (like Arbitrum or Optimism) must post the full transaction data (calldata) for every transaction to L1, as their fraud proofs need the raw data to be available for verification during the 7-day challenge window. This makes ZK Rollups like zkSync and StarkNet more data-efficient.
CHOOSE YOUR PRIORITY
Decision Framework: Choose Based on Your Use Case
ZK Rollups (e.g., zkSync, Starknet) for Cost
Verdict: Superior long-term cost structure. Strengths: Data Availability (DA) costs are the primary expense. By leveraging validity proofs, ZK Rollups can use external DA layers (e.g., Celestia, EigenDA) or Ethereum's blob storage (EIP-4844) to minimize L1 posting fees. This creates a predictable, low-cost model for high-throughput applications. Finality is also faster, reducing capital lock-up times. Trade-offs: Prover computation is expensive, but this cost is amortized across all transactions in a batch. For apps with sustained activity, the per-transaction cost is highly competitive.
Optimistic Rollups (e.g., Arbitrum, Optimism) for Cost
Verdict: Simpler, but with higher baseline costs and risk premiums. Strengths: No expensive prover, so fixed costs are lower. However, they must post all transaction data to Ethereum calldata (or a secure DA layer) and maintain a 7-day fraud proof window. This results in higher mandatory L1 data fees and introduces a "cost of trust"—liquidity providers charge premiums for instant withdrawals, indirectly increasing user costs.
verdict
THE ANALYSIS
Verdict: Strategic Recommendations for Architects
Choosing a Data Availability (DA) layer is a foundational decision that defines your rollup's security, cost, and future-proofing.
DA for ZK Rollups excels at immediate finality and cost efficiency because validity proofs allow them to inherit Ethereum's security without the long challenge window. For example, a ZK rollup like zkSync Era can post a single validity proof for thousands of transactions, compressing DA costs. This model is optimal for high-frequency, low-value applications like DEX swaps or gaming where users demand instant, inexpensive withdrawals.
DA for Optimistic Rollups takes a different approach by prioritizing flexibility and lower computational overhead during normal operations. This results in a trade-off: lower proving costs during block production but a mandatory 7-day challenge period for security. Protocols like Arbitrum and Optimism leverage this to support complex, general-purpose smart contracts, where the cost of generating ZK proofs for every state transition can be prohibitive.
The key trade-off is between operational cost structure and trust assumptions. If your priority is minimizing time-to-finality and building a highly scalable payments/DeFi niche app, choose a ZK rollup with a secure DA layer like Ethereum or Celestia. If you prioritize developer flexibility, supporting arbitrary EVM logic, and can tolerate a week-long withdrawal delay for users, an Optimistic rollup remains the pragmatic choice. The landscape is evolving, with hybrid solutions like validiums (ZK with off-chain DA) and optimiums (Optimistic with off-chain DA) offering further granularity in this spectrum.
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