Senior QA Engineer
Status
London, United Kingdom
Full time
Hybrid
Compensation is not specified
Role
QA Engineer
Description
We are dedicated to making the digital asset world inclusive and secure for all individuals. If you are passionate about contributing to this mission, we invite you to join us.
Established in 2014, Ledger serves as a global digital asset and Web3 platform. Currently, more than 15% of the world's crypto assets are safeguarded through our Ledger Nanos. Located in Paris, Vierzon, the UK, US, Switzerland, and Singapore, Ledger boasts a team exceeding 600 professionals work on diverse products and services. Our primary focus is to enable individuals and businesses to securely purchase, store, exchange, grow, and manage crypto assets, including the famed Ledger hardware wallets — with over 5 million units sold in 180 countries.
We at Ledger embody distinctive values: Pragmatism, Audacity, Commitment, Trust, and Transparency. Our overarching goal is to deliver high-quality products that ensure customer satisfaction.
The Quality Assurance (QA) Engineering team at Ledger plays a pivotal role in safeguarding customer experience, protecting against potential pitfalls such as poor user experience, financial loss, wasted time, and damage to business reputation. The team accomplishes this through active monitoring of quality indicators, holding engineering and product teams accountable, and testing the final product to gauge user experience quality.
As a QA engineer collaborating with one or more product teams, your responsibilities will encompass formulating test strategies for upcoming features, aiding in test execution, and contributing to the development of automated tests. The key activities include estimating, prioritizing, planning, and coordinating testing activities, designing, writing, maintaining, and running functional and regression tests, managing task details and testing scope for multiple projects, performing continuous regression testing, participating in bug management, actively involving in agile meetings with product and development teams, reviewing requirement specifications and technical design documents, and staying abreast of testing tools and methodologies.
Requirements:
- Minimum 5 years of QA experience
- Practical experience with test management tools
- Familiarity with the terminal, shell script, git, and CI/CD environments
- Proficiency in writing automated tests using Playwright or Detox in Javascript
- Flexibility to learn and adapt to new technical skills
- Strong organizational and documentation skills
- Ability to handle multiple complex projects simultaneously
- Proficiency in testing on Windows, macOS, iOS, and Android platforms
- Tech-savvy, curious, and resourceful with strong communication skills
Bonus Skills:
- Background in native applications
- Interest in test automation
- Curiosity in blockchain technology and web3
Benefits:
- Equity opportunities
- Flexible hybrid work policy
- Social events and outings
- Comprehensive health insurance
- Personal development and fitness facilities
- Generous vacation days
- Access to high-performance office equipment
- Transportation reimbursement
- Employee discount on products
We are an equal opportunity employer and welcome applicants regardless of gender, ethnicity, religion, sexual orientation, social status, disability, or age.
Skills Required
Ledger
Website
www.ledger.comCompany size
Not specified
Location
United States
Description
Not specified
Status
Limechain
Smart Contract Engineer
Sofia, Bulgaria
Sofia, Bulgaria
Full time
Remote
About Role:
We are looking for a Smart Contract Engineer to join our blockchain engineering team and help build secure, production-grade decentralized applications and protocols.
In this role, you will design, develop, test, and review smart contracts across EVM and other blockchain ecosystems. You will work closely with blockchain engineers, auditors, and product teams to build reliable smart contract systems, identify vulnerabilities, and improve protocol security, architecture, and performance.
This role is ideal for someone with strong hands-on smart contract experience, deep knowledge of DeFi mechanics, and a security-first engineering mindset.
Responsibilities:
Design, develop, and maintain smart contracts for DeFi and blockchain applications
Write clean, secure, well-tested Solidity code
Build automated tests using Foundry, Hardhat, or Anchor
Review smart contract logic, architecture, and protocol design
Identify security risks, logic flaws, economic attack vectors, and trust assumptions
Analyze common DeFi risks such as flash loans, oracle manipulation, MEV, sandwich attacks, and governance risks
Use tools such as Slither, Mythril, Echidna, Halmos, Manticore, Aderyn, Certora, and Tenderly
Support audits, remediation, fix verification, and deployment processes
Document technical decisions, security considerations, and implementation details
Requirements:
Strong experience with Solidity and EVM smart contract development
Experience with Foundry and/or Hardhat
Solid understanding of blockchain architecture, DeFi protocols, token standards, and smart contract security
Ability to write secure, efficient, maintainable smart contract code
Experience testing, debugging, and reviewing smart contracts
Knowledge of common vulnerabilities: reentrancy, access control issues, oracle risks, precision errors, and upgradeability risks
Familiarity with OpenZeppelin and secure development practices
Strong analytical thinking and clear communication skills
Nice to Have:
Experience with Rust, TypeScript, Solana, Anchor, or NEAR
Experience building or auditing production DeFi protocols
Knowledge of formal verification, fuzz testing, symbolic execution, or property-based testing
Experience with Ethereum, Arbitrum, Base, Optimism, Solana, NEAR, MultiversX, or other ecosystems
Experience with AMMs, lending protocols, bridges, staking systems, or governance mechanisms
What We Offer:
Healthcare
Company computer
Paid holidays
Flexible hours
Competitive salary
Career growth
Friendly team
We are looking for a Smart Contract Engineer to join our blockchain engineering team and help build secure, production-grade decentralized applications and protocols.
In this role, you will design, develop, test, and review smart contracts across EVM and other blockchain ecosystems. You will work closely with blockchain engineers, auditors, and product teams to build reliable smart contract systems, identify vulnerabilities, and improve protocol security, architecture, and performance.
This role is ideal for someone with strong hands-on smart contract experience, deep knowledge of DeFi mechanics, and a security-first engineering mindset.
Responsibilities:
Design, develop, and maintain smart contracts for DeFi and blockchain applications
Write clean, secure, well-tested Solidity code
Build automated tests using Foundry, Hardhat, or Anchor
Review smart contract logic, architecture, and protocol design
Identify security risks, logic flaws, economic attack vectors, and trust assumptions
Analyze common DeFi risks such as flash loans, oracle manipulation, MEV, sandwich attacks, and governance risks
Use tools such as Slither, Mythril, Echidna, Halmos, Manticore, Aderyn, Certora, and Tenderly
Support audits, remediation, fix verification, and deployment processes
Document technical decisions, security considerations, and implementation details
Requirements:
Strong experience with Solidity and EVM smart contract development
Experience with Foundry and/or Hardhat
Solid understanding of blockchain architecture, DeFi protocols, token standards, and smart contract security
Ability to write secure, efficient, maintainable smart contract code
Experience testing, debugging, and reviewing smart contracts
Knowledge of common vulnerabilities: reentrancy, access control issues, oracle risks, precision errors, and upgradeability risks
Familiarity with OpenZeppelin and secure development practices
Strong analytical thinking and clear communication skills
Nice to Have:
Experience with Rust, TypeScript, Solana, Anchor, or NEAR
Experience building or auditing production DeFi protocols
Knowledge of formal verification, fuzz testing, symbolic execution, or property-based testing
Experience with Ethereum, Arbitrum, Base, Optimism, Solana, NEAR, MultiversX, or other ecosystems
Experience with AMMs, lending protocols, bridges, staking systems, or governance mechanisms
What We Offer:
Healthcare
Company computer
Paid holidays
Flexible hours
Competitive salary
Career growth
Friendly team
Payment in Crypto
TA Quant
Senior Rust Developer
Full time
Remote
About the Role
We're looking for a Senior Rust Developer to join our core engineering team and own the systems that sit closest to the market. This means low-latency order execution engines, high-throughput market data pipelines, real-time streaming infrastructure, and integrations with both centralized and decentralized exchanges. Every millisecond and every line of code matters here, and you'll be the person making sure it all holds up under pressure. This is not a role for someone who wants to write Rust adjacent to trading. You'll be building the backbone of live production systems where correctness, safety, and raw performance have direct P&L consequences. You'll work alongside quantitative researchers and other engineers to implement and deploy strategies, and you'll have meaningful input into the infrastructure decisions that shape how we build and scale. If you've spent years pushing Rust to its limits in high-performance environments and you want that work to matter in real markets in real time, this is the role.
Responsibilities
Design, build, and maintain high-throughput, low-latency trading systems in Rust
Develop and optimize order execution engines, market data feeds, and real-time processing pipelines
Build reliable integrations with centralized and decentralized exchanges across CEX and DEX environments
Architect systems for real-time streaming data and WebSocket communication at scale
Write safe, well-tested concurrent code leveraging async runtimes including Tokio and async-std
Collaborate with quantitative researchers to implement and deploy trading strategies into production
Profile, benchmark, and eliminate performance bottlenecks across critical system paths
Contribute to infrastructure decisions around deployment, observability, and fault tolerance
Requirements
5+ years of professional software engineering experience
2+ years building and maintaining production systems in Rust, and you will be tested on it
Deep command of Rust's ownership model, lifetimes, traits, and async patterns
Experience with high-performance networking including TCP/UDP, WebSockets, and gRPC
Strong understanding of concurrency primitives and lock-free data structures
Familiarity with financial systems, trading platforms, or real-time data pipelines
Linux systems programming and performance tuning experience
Comfortable working independently in a fast-paced, remote-first environment
Nice to Have
Experience with cryptocurrency exchanges, DeFi protocols, or blockchain RPC nodes
Knowledge of FIX protocol or other financial messaging standards
Open-source Rust contributions
Experience with FPGA or kernel-bypass networking such as DPDK or io_uring
Familiarity with quantitative trading concepts including order books and market microstructure
Infrastructure experience with Docker, Kubernetes, Terraform, or Prometheus/Grafana
We're looking for a Senior Rust Developer to join our core engineering team and own the systems that sit closest to the market. This means low-latency order execution engines, high-throughput market data pipelines, real-time streaming infrastructure, and integrations with both centralized and decentralized exchanges. Every millisecond and every line of code matters here, and you'll be the person making sure it all holds up under pressure. This is not a role for someone who wants to write Rust adjacent to trading. You'll be building the backbone of live production systems where correctness, safety, and raw performance have direct P&L consequences. You'll work alongside quantitative researchers and other engineers to implement and deploy strategies, and you'll have meaningful input into the infrastructure decisions that shape how we build and scale. If you've spent years pushing Rust to its limits in high-performance environments and you want that work to matter in real markets in real time, this is the role.
Responsibilities
Design, build, and maintain high-throughput, low-latency trading systems in Rust
Develop and optimize order execution engines, market data feeds, and real-time processing pipelines
Build reliable integrations with centralized and decentralized exchanges across CEX and DEX environments
Architect systems for real-time streaming data and WebSocket communication at scale
Write safe, well-tested concurrent code leveraging async runtimes including Tokio and async-std
Collaborate with quantitative researchers to implement and deploy trading strategies into production
Profile, benchmark, and eliminate performance bottlenecks across critical system paths
Contribute to infrastructure decisions around deployment, observability, and fault tolerance
Requirements
5+ years of professional software engineering experience
2+ years building and maintaining production systems in Rust, and you will be tested on it
Deep command of Rust's ownership model, lifetimes, traits, and async patterns
Experience with high-performance networking including TCP/UDP, WebSockets, and gRPC
Strong understanding of concurrency primitives and lock-free data structures
Familiarity with financial systems, trading platforms, or real-time data pipelines
Linux systems programming and performance tuning experience
Comfortable working independently in a fast-paced, remote-first environment
Nice to Have
Experience with cryptocurrency exchanges, DeFi protocols, or blockchain RPC nodes
Knowledge of FIX protocol or other financial messaging standards
Open-source Rust contributions
Experience with FPGA or kernel-bypass networking such as DPDK or io_uring
Familiarity with quantitative trading concepts including order books and market microstructure
Infrastructure experience with Docker, Kubernetes, Terraform, or Prometheus/Grafana
Payment in Crypto
Keras Labs
Senior Software Engineer
Full time
Remote
Role OverviewKeras Labs is seeking a high-performing Blockchain Engineer to design, build, and scale smart contract systems for a hybrid AMM + perpetual trading platform powered by AI agents.This role also includes building and deploying standard token contracts (ERC20/BEP20) and supporting core on-chain infrastructure in a fast-paced, product-driven environment. Core ResponsibilitiesBuild and maintain smart contracts (Solidity / Rust)Develop and deploy ERC20 / BEP20 (or equivalent EVM) tokensImplement token logic (minting, burning, access control)Build core protocol modules (liquidity, trading, vaults)Integrate price oracles and on-chain data sourcesOptimize contracts for gas efficiency and performanceCollaborate with frontend, product, and research teamsSupport testing, audits, and deployment workflowsMonitor protocol performance and on-chain activity RequirementsStrong proficiency in Solidity (EVM) and/or RustExperience deploying ERC20 / BEP20 or similar token standardsFamiliarity with smart contract testing (Foundry, Hardhat)Understanding of contract security best practicesStrong system design and problem-solving skillsComfortable working in a fast-paced, remote environment Nice to HaveExperience with DeFi protocols (DEX, perps, lending)Understanding of AMM models and perpetual mechanicsExperience building trading systems or financial primitivesExperience with oracles (Chainlink, Pyth, etc.)Exposure to AI agents or automated trading systemsOpen-source contributions in Web3 / DeFi Compensation & BenefitsPerformance Bonus: Annual incentive structureBenefits: Remote-first flexibility, high ownership, impact-driven culture
Payment in Crypto
TA Quant
Quantitative Researcher
Full time
Remote
We're looking for a Quant Researcher to join us remotely and take direct ownership of the research lifecycle, from raw data exploration all the way through to live strategy deployment. You'll work closely with our trading and engineering teams to develop, test, and continuously refine the models and algorithms that drive real P&L outcomes across crypto markets. This is a high-ownership role with meaningful exposure to live markets from day one. You won't be running support research in the background, you'll be a core contributor shaping the strategies we actually trade. That means working with large and often unconventional datasets, identifying exploitable statistical patterns in volatile and illiquid market conditions, and translating rigorous mathematical research into production-ready code that performs when it counts.
Responsibilities
Develop, backtest, and continuously improve quantitative trading models and algorithms, translating mathematical insights into production-ready code
Collaborate with trading and development teams to refine existing strategies and build new ones with a direct focus on P&L impact
Work through large and complex datasets to identify patterns, validate hypotheses, and stress-test models against real market conditions
Conceptualize valuation frameworks, improve mathematical models, and maintain strategy performance in live environments
Conduct ongoing statistical research into crypto market microstructure and price dynamics using both conventional and unconventional data sources
Requirements
Advanced degree in mathematics, statistics, physics, computer science, or a related quantitative field
Strong proficiency in probability and statistics, including time-series analysis, machine learning, and pattern recognition applied to financial data
Hands-on programming experience in Python, with familiarity in R or MATLAB and ideally some exposure to compiled languages like C++
Prior experience in crypto markets, digital asset trading, or algorithmic finance
Proven ability to work in a data-driven research environment with minimal direction
Rigorous, evidence-based approach to problem-solving with the ability to move quickly from hypothesis to testable implementation
Responsibilities
Develop, backtest, and continuously improve quantitative trading models and algorithms, translating mathematical insights into production-ready code
Collaborate with trading and development teams to refine existing strategies and build new ones with a direct focus on P&L impact
Work through large and complex datasets to identify patterns, validate hypotheses, and stress-test models against real market conditions
Conceptualize valuation frameworks, improve mathematical models, and maintain strategy performance in live environments
Conduct ongoing statistical research into crypto market microstructure and price dynamics using both conventional and unconventional data sources
Requirements
Advanced degree in mathematics, statistics, physics, computer science, or a related quantitative field
Strong proficiency in probability and statistics, including time-series analysis, machine learning, and pattern recognition applied to financial data
Hands-on programming experience in Python, with familiarity in R or MATLAB and ideally some exposure to compiled languages like C++
Prior experience in crypto markets, digital asset trading, or algorithmic finance
Proven ability to work in a data-driven research environment with minimal direction
Rigorous, evidence-based approach to problem-solving with the ability to move quickly from hypothesis to testable implementation
Payment in Crypto
Michael Har
Junior / Middle Metaverse Developer (Unity / Web3 / VR)
Manzhouli, China
Manzhouli, China
Full time
Remote
We are looking for a Metaverse Developer to help build interactive virtual environments and immersive digital experiences. The role involves developing 3D worlds, integrating Web3 technologies, and working with modern tools for real-time applications.
You will work with Unity, WebGL, and blockchain technologies to create engaging metaverse features and optimize them for performance across different devices. The developer will collaborate with designers and backend engineers to deliver scalable and stable products.
Requirements include experience with Unity and C#, understanding of 3D development, Web3 or blockchain basics, and familiarity with Git and API integration. Experience with VR/AR, NFTs, or multiplayer systems is a plus.
We offer remote work, flexible hours, crypto payments, and the opportunity to build innovative metaverse products.
You will work with Unity, WebGL, and blockchain technologies to create engaging metaverse features and optimize them for performance across different devices. The developer will collaborate with designers and backend engineers to deliver scalable and stable products.
Requirements include experience with Unity and C#, understanding of 3D development, Web3 or blockchain basics, and familiarity with Git and API integration. Experience with VR/AR, NFTs, or multiplayer systems is a plus.
We offer remote work, flexible hours, crypto payments, and the opportunity to build innovative metaverse products.
Payment in Crypto