QA Engineer - Vault

Paris, France
Full time
Compensation is not specified
QA Engineer
Work Experience
More than 3 years

We're making the world of digital assets accessible and secure for everyone. 

Join the mission.

Founded in 2014, Ledger is the global platform for digital assets and Web3. Over 15% of the world’s crypto assets are secured through our Ledger Nanos. Headquartered in Paris and Vierzon, with offices in the UK, US, Switzerland and Singapore, Ledger has a team of more than 700 professionals developing a variety of products and services to enable individuals and companies to securely buy, store, swap, grow and manage crypto assets – including the Ledger hardware wallets line with more than 5 millions units already sold in 180 countries. 

At Ledger, we embody the values that make us unique: Pragmatism, Audacity, Commitment, Trust and Transparency. Have a look at our Origins video here.

The QA Engineer will work to validate current and future functionalities. Working closely with the QA Expert/Lead and developers to identify possible test scenarios, evaluate the need for more extensive testing methods and participate in the development of the team into agile testing methodology.

Your mission

  • Elaborate, maintain and implement detailed test plans, help define acceptance criteria for different scenarios.
  • Provide complete and detailed analysis of failing tests to help engineering teams understand better the corrective actions to be implemented.
  • Assess risk from test results and alert in time the squad of potential issues.
  • Ensure good communication with different stakeholders through thorough and well structured reports.
  • Apply extensive testing methodologies to assure quality of our products.
  • Being able to create/apply extensive exploratory testing to identify possible risks.
  • Engage squad team in agile testing methodology, sharing knowledge and being able to create debate on current practices.
  • Work with QA automation team to create specifications and acceptance criteria for test scenarios & tools.
  • Be active in the use of automated testing solutions 

What we’re looking for

  • 5+  years of experience in software quality assurance
  • Good knowledge of Unix commands
  • Team work spirit, great organizational and communication skills
  • Fluent English is a must
  • Experience/knowledge in blockchain and IoT technology is appreciated
  • Proficient in black box, grey box testing approaches
  • Good knowledge of development processes, agile methodology.
  • Experience with AWS, Docker containers
  • Engineering degree
Skills Required
Company size
Not specified
United States
Ledger is a leader in security and infrastructure solutions for cryptocurrencies and blockchain applications. We are constantly looking for innovative, talented people to join our team.

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Solutions Engineer

Los Angeles, USA
Los Angeles, USA
Full time
Solutions Designer - Games Studio

Genies, the leading avatar technology company, is seeking a Solutions Designer to join our dynamic Games Studio. As a Solutions Designer, you will play a vital role in shaping the future of mobile gaming experiences. Collaborating with a creative and collaborative team, you will leverage your experience in solutions design to create engaging and immersive gameplay. The ideal candidate has a proven track record in shipping multiple mobile games and thrives in autonomous and collaborative environments.

At Genies, we are at the forefront of the digital avatars and gaming industry, empowering users to interact with hyper-realistic avatars in captivating virtual experiences. If you're passionate about pushing the boundaries of avatars, gaming, and creating captivating user experiences, we invite you to join our team!


Design, implement, balance, and support the Traits and Things systems.

Collaborate closely with internal and external game development teams to support the development and iteration of major systems.

Design and develop other major systems and mechanics.

Utilize scripting tools, spreadsheets, and other technologies to implement, tune, and balance complex gameplay systems.

Maintain a user-centric approach, prioritizing user satisfaction and retention in design decisions.

Collaborate with artists, engineers, and product managers to integrate gameplay elements and features successfully.

Create and update detailed design documentation, including game mechanics, systems, and features.


Proven experience in designing and implementing large, complex game systems such as economy design and progression systems.

Passion for analyzing and understanding intricate constructs.

Ability to communicate complex systems clearly and concisely.

Deep passion for games, with a keen interest in playing, analyzing, and discussing them.

Successful track record in shipping multiple mobile games.

Creative mindset with a drive to push the boundaries of mobile gaming.

In-depth knowledge of game systems design, progression, and monetization strategies.

Bachelor's degree in Game Design, Computer Science, or related field (Masters in Computer Science is a plus).

Strong communication and teamwork skills.

Self-motivated, proactive, and able to work independently.

What We Offer:

Genies is a well-funded startup that cares about the growth and success of our employees. You will have the opportunity to face exciting challenges and opportunities in a growing startup environment. Your base salary will depend on factors such as your professional background, skills, and location. Additionally, full-time employees may receive equity compensation along with a comprehensive health, wellness, and benefits package.

Starting Salary Range: $180,000 to $250,000

Why You'll Love Working at Genies:

Learn and grow with a supportive and collaborative team while shaping your career.

Flexible working hours and work from home policy.

Enjoy the perks and culture of a startup with stable funding.

Comprehensive health insurance, dental and vision insurance for you and your family.

Competitive salaries for all full-time employees.

Generous paid time off, including parental leave, sick leave, holidays, bereavement leave, and jury duty.

Health and wellness support with monthly wellness reimbursement.

Work in a brand new, vibrant, and fun office space.

Genies is an equal opportunity employer committed to creating an inclusive work environment free from discrimination and harassment. We value diversity, inclusion, and aim to foster a sense of belonging for all.

Internship Program 2023

Full time
At Nethermind, we are a team of highly skilled builders and researchers who specialize in various areas within the blockchain industry. Our expertise includes Ethereum Protocol Engineering, Layer-2 solutions, Decentralized Finance (DeFi), Miner Extractable Value (MEV), Smart Contract Development, Security Auditing, and Formal Verification.

Collaborating with renowned companies such as Ethereum Foundation, StarkWare, Gnosis Chain, Aave, Flashbots, xDai, Open Zeppelin, Forta Protocol, Energy Web, POA Network, and more, we are dedicated to solving the most challenging problems in the blockchain space.

We actively contribute to Ethereum core development, including EIP's and network upgrades, working together with the Ethereum Foundation and other client teams.

With a remote team of nearly 200 individuals from over 45+ countries, we offer an internship program that provides students and graduates worldwide with a unique opportunity to learn about the inner workings of Ethereum and make tangible contributions to its evolution. The program, which has received a grant from the Ethereum Foundation, allows interns to work on exciting and challenging projects and offers full autonomy in choosing projects, skills to develop, and teams to collaborate with.

The internship program covers various areas such as Blockchain Core Engineering, Cryptography Research, DevOps, Security, L2 Tooling, and DeFi Research & Development. It is a paid internship.

To learn more about the engineering groups you can join as an intern, visit our website or connect with us directly on Discord.

Please note that due to high demand, we have limited spaces available for the upcoming months and will only be interviewing and hiring top candidates. However, we will continue to accept applications and consider candidates who are the best fit for Nethermind.

If you are not selected initially, we encourage you to continue developing your skills and knowledge and reapply in the future. We appreciate the interest and talent of all applicants.

If you are interested in the internship program, please read our disclaimer regarding the storage and processing of your personal information for recruitment purposes.

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Senior Data Scientist

Full time
At Nethermind, we are a team of experts in various domains within the blockchain space. Our focus areas include Ethereum Protocol Engineering, Layer-2 solutions, Decentralized Finance (DeFi), Miner Extractable Value (MEV), Smart Contract Development, Security Auditing, and Formal Verification. We collaborate with renowned companies such as Ethereum Foundation, StarkWare, Gnosis Chain, Aave, Flashbots, xDai, Open Zeppelin, Forta Protocol, Energy Web, and POA Network. As a team of nearly 200 individuals working remotely from over 45 countries, we actively contribute to Ethereum core development and network upgrades.

We are currently seeking a Senior Data Scientist to contribute to the Forta ecosystem. In this role, you will analyze blockchain attack data, develop data science solutions to understand and predict attacks and scams, and support the consumption of alerts. You will collaborate with the data science and academic research community to bring innovative solutions to Forta through prototyping, educational content, research papers, data curation, and data science competitions.

The ideal candidate is passionate about leveraging data science to protect the web3 ecosystem and is excited to collaborate with a global data science and research community.


Analyze blockchain and attack data

Prototype various models to detect attacks, rank alerts, and provide context to alert data

Empower the data science community to protect web3 through data set curation, prototyping, and contest preparation

Collaborate with the data science and engineering community to enhance Forta Network's data science and machine learning capabilities

Facilitate research collaborations with the data science and academic research community

Educate the broader community on data science approaches to web3 through research papers, blog posts, conference talks, and social media presentations


Minimum of 5 years of professional experience in Machine Learning, Natural Language Processing, Deep Learning, Anomaly Detection, Clustering, and Time Series Analysis

Proficiency in Python and familiarity with other scripting languages such as R

Experience with libraries like Pandas, Keras, Pytorch, and Scikit-learn for building ML models

Strong attention to detail, self-discipline, and drive for results

Ability to work in ambiguous situations and with geographically distributed teams

Bachelor's degree in Statistics, Mathematics, Computer Science, Engineering, or related technical field (or equivalent experience)

Excellent writing and communication skills

Ability to simplify complex technical topics for diverse audiences

Strong organizational skills and ability to manage time effectively

Passion and/or experience in open-source, cybersecurity, or a related technical industry is preferred

Technical knowledge of blockchain, DeFi, and the Ethereum ecosystem is desired

At Nethermind, we are committed to creating a diverse workforce and value different perspectives. We are an equal opportunity employer that celebrates uniqueness in our employees. Join us in our mission!


Data Science and Machine Learning on Forta

Kaggle Competition: It's Time to Protect Web3 with Forta

Forta Labeled Datasets

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CTO - Twinstake

London, UK
London, UK
Full time

What is our mission?

We are a highly skilled team of builders and researchers specializing in various areas of expertise within the blockchain space. This includes Ethereum Protocol Engineering, Layer-2, Decentralized Finance (DeFi), Miner Extractable Value (MEV), Smart Contract Development, Security Auditing, and Formal Verification.

In our pursuit to solve complex challenges in the blockchain industry, we collaborate with renowned companies such as Ethereum Foundation, StarkWare, Gnosis Chain, Aave, Flashbots, xDai, Open Zeppelin, Forta Protocol, Energy Web, POA Network, among others.

As active contributors to the Ethereum core development, EIP's, and network upgrades alongside the Ethereum Foundation and other client teams, our team of nearly 200 individuals work remotely from over 45 countries.

To see all our current job openings, visit:

About Twinstake:

Twinstake is a top institutional staking provider with a rich history in the institutional market. Our team combines deep crypto expertise and technology from our core developers and industry veterans.

As a technology-driven organization, we are looking for a Chief Technology Officer (CTO) to play a strategic role. As the CTO, you will provide leadership and technical expertise to drive the development and implementation of our staking infrastructure and related products. You will lead a team of talented engineers and developers, working closely with cross-functional stakeholders to design, build, and maintain a scalable and secure infrastructure platform.

Responsibilities of the CTO:

Evaluate the strategic vision and recommend technological solutions to maintain Twinstake's leadership position in the industry.

Take charge of the technology roadmap, ensuring alignment with overall business objectives.

Drive the architecture, scalability, and implementation of Twinstake's infrastructure and data platforms to meet the growing demand for staking services.

Lead the design, development, and deployment of technological solutions, including new product launches, strategic integrations, and onboarding of new assets.

Establish and enforce development and deployment methodologies, coding standards, and quality assurance processes to deliver robust and reliable solutions.

Oversee the security and privacy aspects of the infrastructure, implementing best practices and ensuring compliance with relevant regulations.

Manage and mentor a team of engineers and developers, fostering a culture of innovation, collaboration, and continuous learning.

Collaborate with cross-functional teams such as product management, operations, and security to ensure successful delivery and maintenance of Twinstake's technology.

Stay up-to-date with industry trends and emerging technologies, assessing their potential integration into the company's infrastructure.

Requirements for the role:

Exceptional leadership and communication skills, with the ability to explain complex technical concepts to both technical and non-technical stakeholders.

Prior experience as a CTO, Technical Director, or similar leadership position in a technology-driven organization.

Deep understanding of blockchain technology, specifically staking and consensus algorithms.

Strong expertise in on-premise infrastructure design, implementation, and management, with knowledge of traditional data center technologies, virtualization, server hardware, and networking.

Proficiency in cloud computing platforms such as AWS, Azure, or Google Cloud, and containerization technologies like Docker and Kubernetes.

Familiarity with DevOps and SRE practices, continuous integration/continuous delivery (CI/CD), and infrastructure automation.

Knowledge of smart contract development and experience with programming languages such as Solidity.

Proficiency in programming languages commonly used in infrastructure development, such as Go, Rust, and Python.

Proven experience in data engineering, including the design and implementation of scalable data pipelines, data warehousing solutions, and data integration strategies using modern technologies.

Deep understanding of cryptographic principles and secure key management.

Familiarity with cybersecurity principles for securing distributed systems.

Track record of successfully delivering complex technological solutions, preferably in infrastructure, within budget and timeline constraints.

Nice to have:

Experience working in a fast-paced startup or high-growth environment.

Previous involvement in finance, especially with institutional asset managers.

Experience working with digital asset custodians.

Disclaimer: Please note that the advertised roles are offered by Twinstake UK Limited, not Nethermind. However, the Nethermind team will oversee the initial stage of the recruitment process before passing successful applicants to Twinstake.

Disclaimer: By providing your personal information, you consent to its storage and processing by Demerzel Solutions Limited (t/a Nethermind) (the “Company”) for recruitment purposes. The Company complies with UK GDPR guidelines. For more information, please refer to our privacy policy. Your consent is voluntary, and you can withdraw it at any time. If you have questions or wish to withdraw your consent, contact

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Software Engineer - Java (Exchange Middle Platform)

Hong Kong
Hong Kong
Full time
Who We Are
At OKX, we believe in shaping the future with technology. Established in 2017, OKX is a leading cryptocurrency exchange that offers spot and derivatives trading. Our innovative use of blockchain technology revolutionizes the financial ecosystem by providing diverse products and advanced trading tools. Trusted by over 20 million users worldwide, OKX aims to empower individuals in exploring the world of crypto. In addition to our world-class DeFi exchange, we also have OKX Insights, a research arm at the forefront of cryptocurrency industry trends. With our wide range of crypto products and dedication to innovation, our vision is to create a financial access world driven by blockchain and decentralized finance.

We value our people as much as we value technology. We foster a collaborative culture where teamwork, adaptability, and integrity are celebrated. Our commitment is to create a friendly and inclusive environment for everyone. Regardless of your background, we ensure that all individuals feel appreciated, respected, and have equal opportunities to grow and thrive. We strive to bring out the best in you.
About the Opportunity
About the Team:

The Middle Platform team is responsible for developing the fundamental components of the exchange. This includes the matching engine, real-time market data streaming, and market data analysis. Our team forms the backbone of our industry-leading trading product, serving millions of users.

What You’ll Be Doing:

Design and implement innovative solutions for our comprehensive range of trading products, including spot, futures, perpetual swaps, and options.

Develop real-time market data gateway.

Optimize overall trading architecture for low latency, high availability, and scalability.

What We Look For In You:

Strong educational background in STEM (Science, Technology, Engineering, Mathematics).

Excellent logical thinking and problem-solving abilities.

Proficiency in high-performance Java, asynchronous programming patterns, and network programming.

Familiarity with distributed systems and microservice architecture.

Experience in automated testing and continuous integration.

Willingness to learn all aspects of trading products in both financial and crypto markets, such as spot, futures, swaps, options, and structured products.

Fluency in English and Mandarin.

Nice to have: Knowledge and experience with financial services protocols such as FIX, SBE, ProtoBuf or similar. Previous experience with low latency messaging frameworks like Aeron and Chronicle Queue.

Perks & Benefits:

Competitive total compensation package.

Comprehensive insurance coverage for employees and their dependents.

More perks and benefits will be shared during the application process!