Валентина

VALYA ZAITSEVA
Kharkiv, Ukraine
[відкрити контакти](див. вище в блоці «контактна інформація») | [відкрити контакти](див. вище в блоці «контактна інформація»)
[відкрити контакти](див. вище в блоці «контактна інформація») | https://github.com/ValyaZay | t.me/VallZay

PROFESSIONAL SUMMARY
Software engineer with 5+ years of experience currently specializing in Rust, Solana, and DeFi protocol development.
Focused on building secure, production-grade DeFi systems in Rust and Anchor.
Specialized in lending protocol design, share-based accounting models, PDA architecture, and invariant-driven testing
methodologies using stateful fuzzing (LiteSVM).
Strong emphasis on protocol correctness, adversarial testing, and failure-mode analysis, with additional research
experience in DeFi security and cross-protocol mechanics.

CORE SKILLS
▪ Blockchain: Rust, Solana, Anchor, Program Derived Accounts (PDA), account validation, CPI design, LiteSVM, SPL
Token, Solidity, EVM, Foundry
▪ DeFi Protocol Engineering: Lending protocols, share-based accounting, liquidation mechanics
▪ Trading Infrastructure: Real-time market data processing, WebSocket subscriptions, arbitrage systems, liquidity
pool state tracking, swap mechanics
▪ Security & Testing: Invariant-based design, stateful fuzzing, handler-based testing, adversarial simulation, unit
testing
▪ Languages: Rust, Solidity (EVM), C#, JavaScript/TypeScript, SQL
▪ Systems: Asynchronous Rust (Tokio), distributed systems, event-driven architecture, microservices

PROFESSIONAL EXPERIENCE
Rust Solana Arbitrage Engineer - Personal Arbitrage Engine System
June 2026 – present
▪ Designed and implemented a market scanner and arbitrage engine for monitoring Raydium CPMM dex on Solana
blockchain - the system continuously monitors 20 Raydium CPMM liquidity pools with TVL more than 10000 USD via
WebSocket account subscriptions, recalculates swap outputs in real time after vaults and pools updates
▪ Implemented concurrent event processing using Tokio (tasks, async channels (mpsc)), custom error handling using
‘thiserror’ crate.
▪ Researched Raydium swap mechanics, token vault accounting, and transaction execution to prepare for on-chain
arbitrage - this includes ‘amount out’ recalculation off-chain. The recalculation formula was proved to be true via
Anchor LiteSvm randomized fuzz tests using raydium-cp-swap repository.
The code is on GitHub https://github.com/ValyaZay/my_doer.

Solana Protocol Engineer - Personal DeFi Lending System
Mar 2026 – June 2026
Designed and implemented a production-style Solana lending protocol using Rust and Anchor, with a focus on
correctness, safety, and protocol-level invariants.
▪ Designed full protocol architecture using Program Derived Accounts (PDAs) with strict ownership and validation
rules
▪ Implemented deposit and withdrawal flows using share-based accounting model
▪ Built deterministic asset/share conversion logic with focus on rounding safety and invariant preservation
▪ Developed comprehensive unit test suite covering edge cases, boundary conditions, and multi-user interactions
▪ Built stateful fuzz testing system (LiteSVM) simulating adversarial multi-user sequences and protocol stress
scenarios
▪ Modeled and enforced core invariants: solvency consistency, balance conservation, state transition correctness
▪ Identified and mitigated common Solana smart contract vulnerability patterns including account spoofing, missing
ownership checks, and unsafe CPI assumptions
▪ Built deterministic randomized testing infrastructure with event logging and protocol state reconstruction for
reproducible debugging of Solana DeFi protocol execution
The project is at https://github.com/ValyaZay/proj-xix-app/tree/master/anchor

DeFi Protocol Security Researcher
Oct 2025 – Mar 2026
Performed protocol behavior analysis and designed invariant-based security modeling across DeFi systems.
▪ Analyzed Aave V3/V4 lending and liquidation mechanics, including edge-case behavior under volatility and
boundary conditions
▪ Studied Chainlink oracle behavior across phase transitions and abnormal market conditions
▪ Designed invariant-based fuzzing frameworks used in smart contract audits (Cyfrin, Sherlock), covering lending
protocols, token systems, multisig / timelock systems
▪ Developed handler-based stateful fuzzing simulations for multi-step adversarial scenarios
▪ Investigated time-dependent protocol behavior (interest accrual, liquidation timing, state transitions)

Solidity Smart Contract Developer - Primex Labs (DeFi, Estonia)
May 2022 – Sep 2023
▪ Developed Solidity smart contracts for DeFi trading systems
▪ Integrated DEX protocols into automated trading workflows
▪ Performed contract debugging and on-chain state analysis
▪ Worked with cross-chain transaction and blockchain data APIs

Software Engineer (.NET / Cloud / Distributed Systems)
2019 – 2025
Backend and systems engineering roles focused on distributed systems and event-driven architectures.
▪ Built microservices using ASP.NET Core and event-driven messaging (RabbitMQ)
▪ Designed distributed processing pipelines and real-time systems
▪ Worked with caching, storage, and cloud infrastructure (Azure Functions, Redis, CosmosDB)
▪ Improved system reliability, observability, and debugging in production systems
▪ Applied CQRS and message-driven architectural patterns
Selected projects:
May 2025 – Sep 2025 - .NET Architect & Developer (Personal Cloud Project)
Designed and built a distributed cloud-native application from scratch using microservices architecture. Implemented backend
using Azure Functions with CosmosDB and Redis for caching. Developed frontend with Blazor and integrated storage via Azure
Blob Storage. Focused on system reliability, performance, and clean architecture principles.
Aug 2024 – Feb 2025 - .NET Developer – Vitalerter (Healthcare, Israel)
Developed event-driven microservices processing real-time alerts via RabbitMQ. Implemented automated decision logic based
on incoming data streams and configurable rules. Debugged distributed systems and traced issues across services and data
pipelines. Improved system observability using logging and monitoring tools (Serilog, Elasticsearch).
Feb 2024 – Mar 2024 - .NET Developer – Peanut Trade (DeFi / MEV, Ukraine)
Integrated blockchain bridges for cross-chain arbitrage trading systems. Worked with real-time transaction data and blockchain
APIs (Etherscan, Nethereum).
May 2021 - Sep 2021 - Unity/.NET Developer – Sayollo (GameDev, Israel)
Developed backend features for custom .NET libraries for video advertisement integration into a gameplay using Unity Engine,
C#, .NET Core, Python. Performed code review, debugging and unit testing.
Sep 2020 - May 2021 - Unity Developer – BiniBambini (GameDev, Ukraine)
 Implemented gameplay logic, tested and debugged code and took part in discussions of specifications and requirements.
Created educational projects on design patterns in Unity.
May 2019 – Sep 2020 - .NET Developer – Aimprosoft (Ukraine)
Developed backend services for online video platform using ASP.NET Core. Implemented APIs, database interactions, and
microservices communication patterns. Applied CQRS, gRPC, and cloud storage solutions.

SELECTED SECURITY RESEARCH
Invariant-based fuzzing research (multi-protocol)
Built and applied invariant-driven testing frameworks across multiple DeFi systems. Covered systems include lending
protocols, token contracts, and multisig / timelock mechanisms.
Key contributions:
▪ Designed system-level invariants (solvency, conservation of value, execution correctness)
▪ Built stateful handler-based fuzzing frameworks simulating complex user interactions
▪ Modeled adversarial multi-step execution paths
▪ Discovered edge cases under randomized and extreme conditions
▪ Analyzed time-dependent system behaviors (interest, liquidation timing, state transitions)
GitHub - Invariant-Based Fuzzing Projects:
▪ Aave V4 invariants: https://github.com/ValyaZay/audit-aave4/tree/valya-audit/aave__aave-v4/tests/valya-
invariants
▪ Multisig fuzzing: https://github.com/ValyaZay/audit-multisig-timelock/tree/valya-audit/test/stateFulFuzz
▪ Token invariants: https://github.com/ValyaZay/audit-token-0x/tree/valya-audit/test/invariant

EDUCATION
Master’s Degree in Medicine - V.N. Karazin Kharkiv National University

CERTIFICATION
Microsoft Certified: Azure Developer Associate https://learn.microsoft.com/api/credentials/share/en-us/ValyaZaitseva-
7494/885CC335DF66C91E?sharingId=157EC3488227D746

LANGUAGES
English – Upper Intermediate (B2)
Ukrainian – Native
Russian – Native