Marat Nusurov

Arbitrage Kit

Company: HodlTree
Role: Senior Solidity Developer
Stack: Solidity 0.8.0 · Truffle · Ganache · Mocha · Web3.js · OpenZeppelin
Period: 09/2020 - 05/2021

Overview

Smart contract framework orchestrating atomic arbitrage trades and flash loan interactions across multiple decentralized exchanges. The architecture abstracts protocol-specific complexity through modular connector contracts, enabling seamless execution of sophisticated multi-leg trading strategies across Ethereum and Polygon. Implements delegatecall-based proxy pattern with stateful memory threading to execute complex arbitrage paths atomically without intermediate state mutations. Operated alongside a self-hosted Geth full node for low-latency RPC access in time-sensitive arbitrage execution.

Technical Scope

Multi-DEX Protocol Abstraction

• Unified connector interface for six major DEXs: Uniswap (V2 & V3), Balancer (V1 & V2), Curve (V1 & V2), Bancor, and 0x Protocol
• Protocol-agnostic swap orchestration via modular connector contracts
• Single atomic transaction execution across fragmented liquidity pools
• Direct pool interaction bypassing router overhead for reduced hop count and implicit fees
• Connector-Specific Optimizations:
  • Uniswap V3: Direct swap callbacks with tick-based slippage calculations
  • Uniswap V2: Constant-product formula (x*y=k) with native 0.3% fee handling
  • Curve: StableSwap formula for stablecoin pairs + CryptoSwap (V2) with underlying token support
  • Balancer: Vault abstraction for batch swaps and internal balance management
  • Bancor: Path-based token routing through relay networks
  • 0x: Order structure parsing and protocol fee relay integration

Flash Loan Framework

• Flash loan initiation with callback-based repayment verification
• Integrated callback authorization via stateful memory verification (prevents reentrancy attacks)
• Support for multiple callback patterns: Uniswap V3 direct pool callbacks, Balancer Vault callbacks, and generic liquidity provider callbacks
• Automatic fee calculation and settlement within same transaction

Stateful Execution Pipeline

• ArbMemory contract provides persistent cross-call storage for uint256 and address values
• getId/setId parameter pattern reduces calldata overhead and enables reusable transaction templates
• Delegatecall-based spell orchestration ensures atomic execution without intermediate state mutations
• Callback authorization via max uint256 key prevents unauthorized contract invocation
• Memory-based state threading with auto-cleanup semantics (delete on read) to prevent stale data leaks

Precise Swap Control

• Exact-input and exact-output modes with explicit slippage protection
• Automatic ETH ↔ WETH conversion with minimal code duplication
• Output amount verification and minimum received constraints per swap
• Protocol-specific fee handling (Uniswap 0.3%, Curve dynamics, Bancor relay networks)

Delegatecall-Based Proxy Architecture

• ArbProxy uses assembly-level delegatecall to execute connector logic atomically, preserving contract storage and balance state across sequential operations
• Eliminates wrapper contracts and re-entrancy concerns

Gas Optimizations

• Minimal ERC-20 interface reduces bytecode by ~30% vs. full standard
• Direct pool interaction bypasses router overhead
• Dynamic allowance reuse (approve to max uint256) minimizes state write redundancy
• Inline assembly reduces function call overhead

Key Engineering Decisions

Decision	Rationale
Delegatecall proxy over wrapper contracts	Atomic execution within single contract context eliminates intermediate transfers and reentrancy risks
Modular connectors per DEX	Protocol-specific optimizations (Curve dynamics, Bancor paths, 0x fees) reduce generic overhead
ArbMemory for state threading	Reduces calldata overhead and enables reusable transaction templates for complex multi-leg arbitrage
Flash loan callback patterns	Callback-based repayment verification enables 0-capital arbitrage on both Uniswap V3 and Balancer pools
Direct pool interaction	Bypasses router layers, reducing hop count and implicit protocol fees for maximum spread capture

Links & Archives

• GitHub: Not public (company policy)
• Contracts Deployed: Not public (company policy)

Technical Insights

• Flash loan callbacks authorized via a one-time token. When a flash loan is initiated, the expected caller’s address is written into a dedicated memory slot. The callback reads that slot to verify the caller - and the read destroys the value. Authorization is consumed by the act of checking it, so no explicit cleanup is needed and replay is structurally impossible.

• Same interface for simple and chained swaps. Every connector function accepts an optional memory reference alongside the explicit amount. When the reference is absent, the value travels directly in the call; when present, it is fetched from shared memory and erased after use. This lets the same function handle both a standalone swap and a step inside a multi-hop arbitrage path without any conditional logic in the connector itself.

• Error messages survive proxy indirection. Connector logic runs inside the proxy via low-level delegation, which normally discards revert reasons. The proxy captures the raw failure data and re-throws it verbatim, so debugging a failed arbitrage spell shows the original connector error rather than a generic revert - a deliberate tradeoff of assembly complexity for operational transparency.

• Vanity address generator as companion tooling. CREATE3Factory enables deploying contracts to deterministic addresses regardless of nonce or bytecode — useful for predictable protocol addresses across chains. To generate candidates efficiently, built a companion vanity address generator in C++/OpenCL (GPU-accelerated) and a multithreaded Node.js version, both brute-forcing CREATE3 salts until the output address matched a desired prefix pattern.

See HodlTree page for additional context.