Aztec vs StarkEx: Privacy-Focused zk-Rollup Implementations

Aztec excels at generalized, programmable privacy by building a zk-zkRollup. Its Noir language and encrypted UTXO model allow developers to write private smart contracts where all logic and state are hidden. For example, its testnet has processed over 1.5 million private transactions, demonstrating the scalability of its approach for applications like private DeFi and confidential voting. This positions it as the leading platform for building new, privacy-native dApps from the ground up.

StarkEx takes a different, application-specific approach by providing a validity rollup framework with a built-in privacy component. It offers data availability (DA) modes—including Validium for full privacy—tailored for high-throughput financial applications. This results in a trade-off: immense scale and lower costs for specific use cases (e.g., dYdX processed over 300M trades) but less flexibility for arbitrary private logic. Its strength is in scaling and securing existing financial primitives like spot trading and NFTs with optional confidentiality.

The key trade-off: If your priority is building novel, fully private applications with custom logic, choose Aztec. If you prioritize scaling a high-volume financial application (like an exchange or NFT marketplace) with robust, audited privacy for balances and trades, choose StarkEx.

Aztec excels at providing universal, programmable privacy because its architecture is built from the ground up for private smart contracts. Its zk.money (now Aztec Connect) protocol demonstrated the ability to batch private DeFi interactions, achieving significant gas savings (up to ~75% vs. L1) for users. The upcoming Aztec 3.0 with its Noir language aims to make private dApp development accessible, positioning it as the go-to for applications like private voting, confidential DAO treasuries, or stealth payments where privacy is the default state for all logic.

StarkEx takes a different approach by offering high-throughput, application-specific privacy on a per-asset basis. This results in a trade-off: it sacrifices universal programmability for proven, production-scale performance. Validiums like Immutable X and dYdX leverage StarkEx to process over 9,000 TPS for NFT minting and perpetual swaps, with sub-$0.01 fees, but privacy is an opt-in feature primarily for designated assets (e.g., privacy for USDC or a specific game item) rather than a default for all contract logic.

The key architectural divergence: Aztec uses a UTXO-based model for inherent privacy, while StarkEx employs a hybrid account/UTXO model optimized for scalability of specific operations. This makes Aztec more flexible for novel private logic but StarkEx more efficient for scaling predefined transaction types like trades or transfers.

The ecosystem and maturity factor: StarkEx benefits from the battle-tested Cairo language and the broader Starknet ecosystem, with over $1.3B in secured value across its validiums. Aztec is pioneering a new stack with Noir, offering greater long-term flexibility for developers but with a newer, less proven toolchain. Integration complexity is generally higher with Aztec's custom circuit requirements.

Strategic Decision: Choose Aztec if your protocol's core value proposition is unconditional privacy and composability for complex, custom smart contract logic (e.g., a private AMM or lending protocol). Choose StarkEx if you need to scale a high-volume application (like an NFT marketplace or DEX) and require optional privacy features or data availability modes (Validium vs. Rollup) for specific assets, leveraging its production-grade throughput and lower immediate integration overhead.