Senior Software Engineer
Barcelona, Spain
Full time
Office
Compensation is not specified
Role
Software Engineer
Description
About Keyfactor
Our goal is to create a connected society built on trust, with a focus on identity-first security for both machines and humans. Keyfactor is dedicated to helping organizations quickly establish and maintain digital trust at scale. With over 1,500 trusted clients globally, we are consistently recognized as a Best Place to Work, thanks to our exceptional team nurturing our culture as we expand. We invite you to consider a future with Keyfactor!
Location: Spain; Barcelona
Experience Requirements: IC4 – Advanced
Job Function: Engineering
Employment Type: Full-Time
Industry: Computer & Network Security
Brief Overview
As a Senior Software Engineer at Keyfactor, you will be responsible for developing and maintaining software applications, implementing new features, and ensuring quality code. This role also involves collaborating with team members to design and troubleshoot complex solutions.
Key Responsibilities
- Develop, implement, and maintain software features and functions
- Conduct code reviews, pull requests, and ensure coding standards compliance
- Collaborate with cross-functional teams to solve complex problems
- Contribute to enhancing software development processes and practices
- Identify and resolve technical issues and performance bottlenecks
- Support and guide junior engineers
- Work closely with Quality Assurance teams when needed
- Participate in both internal and external product support
- Assist in technical documentation and project reporting
- Engage in Agile ceremonies and contribute to iterative development processes
Minimum Qualifications, Education, and Skills
- Bachelor’s degree in Computer Science, Engineering, or related field, or equivalent experience
- Strong background in software engineering or related field
- Strategic thinking, strong problem-solving skills, and proficiency in relevant tools and technologies
- Proficiency in design patterns, strong architectural skills, and advanced debugging capabilities
- Experience leading complex projects and driving strategic initiatives
- Ability to mentor team members, take on complex tasks, and encourage technical improvements
- Deep understanding of industry trends, company strategy, and cross-functional processes
- Extensive knowledge of software architecture principles, code optimization, and continuous integration practices
Compensation
Salary is based on experience and will be commensurate.
Culture, Career Opportunities, and Benefits
At Keyfactor, we continually strive to improve and offer opportunities for personal and professional growth. We provide a balance of autonomy and structure to foster an entrepreneurial environment that encourages creativity and innovation. Our initiatives support our special culture:
- Second Fridays (company-wide day off on the second Friday of every month)
- Comprehensive benefit coverage for you and your dependents
- Generous paid parental leave
- Employee-focused initiatives like Key Contributors & Culture Committees
- DIVERSE Commitment for inclusivity and diversity promotion
- Wellbeing resources, mindfulness app membership, Wellness Wednesdays
- Global Volunteer Day, volunteer time off, and company non-profit matching
- Unlimited time off (US) and competitive paid time off globally
- Monthly talent development and Cross Functional meetings for professional growth
- Regular All Hands meetings with group gatherings
Core Values
Our core values are central to how we operate and what we look for in every team member. They are:
- Trust is paramount
- Customers are core
- Innovation never stops, it only accelerates
- We deliver with agility
- United by respect
- Teams make "it" happen
Keyfactor is an equal opportunity employer, including veterans and individuals with disabilities.
Reasonable Accommodation: Applicants with disabilities can contact the People team for accommodation arrangements.
Stay Safe. Be Kind. Brush your hair before the Zoom call!
Skills Required
Keyfactor
Website
www.keyfactor.comCompany size
Not specified
Location
United States
Description
Not specified
Lumixion
DApp & Smart Contract Developer (Vesting Platform)
Full time
Remote
We are looking for a skilled DApp & Smart Contract Developer to enhance and stabilize our client’s crypto vesting platform. You will diagnose existing issues, improve performance, deliver new features, and ensure seamless coordination between smart contracts and the front end.
This role is ideal for someone who thrives in fast-moving environments, values clean and secure code, and understands the nuances of blockchain-based application architecture.
Responsibilities
Diagnose and resolve issues in vesting smart contracts and their front-end integrations.
Implement new features and system enhancements to improve UX and overall platform performance.
Maintain smooth interaction between the web interface and deployed smart contracts.
Conduct testing, audits, and deployments across testnet and mainnet environments.
Optimize contract logic for performance, security, and gas efficiency.
Collaborate with our engineering team to identify pain points and deliver stable, secure solutions.
Requirements
Proven experience building full-stack decentralized applications.
Strong proficiency in Solidity, JavaScript/TypeScript, and modern frameworks (Angular, React, or Vue).
Hands-on experience with Hardhat or Foundry for smart contract development and testing.
Familiarity with Ethers.js or Web3.js for blockchain interaction layers.
Solid understanding of Ethereum, Polygon, or other EVM-compatible chains.
Experience integrating wallets such as MetaMask and managing on-chain/off-chain data flows.
Strong debugging skills, attention to detail, and a security-first mindset.
Nice to Have
Experience with smart contract security audits and gas optimization techniques.
Knowledge of Node.js-based backend services or API integration layers.
Previous experience with vesting, staking, or token distribution mechanisms.
Project Scope
This role supports a short-to-mid-term initiative focused on stabilizing and enhancing an existing crypto vesting platform. High-performing developers may have opportunities for ongoing collaboration across additional blockchain and product engineering projects.
Hiring Process
Technical Assessment - Selected candidates will complete a short, clearly scoped technical exercises designed solely to evaluate coding approach and smart contract knowledge.
CTO interview - A final discussion to evaluate technical reasoning, architectural thinking, and team fit. Successful candidates may receive an offer through Contra following this conversation.
This role is ideal for someone who thrives in fast-moving environments, values clean and secure code, and understands the nuances of blockchain-based application architecture.
Responsibilities
Diagnose and resolve issues in vesting smart contracts and their front-end integrations.
Implement new features and system enhancements to improve UX and overall platform performance.
Maintain smooth interaction between the web interface and deployed smart contracts.
Conduct testing, audits, and deployments across testnet and mainnet environments.
Optimize contract logic for performance, security, and gas efficiency.
Collaborate with our engineering team to identify pain points and deliver stable, secure solutions.
Requirements
Proven experience building full-stack decentralized applications.
Strong proficiency in Solidity, JavaScript/TypeScript, and modern frameworks (Angular, React, or Vue).
Hands-on experience with Hardhat or Foundry for smart contract development and testing.
Familiarity with Ethers.js or Web3.js for blockchain interaction layers.
Solid understanding of Ethereum, Polygon, or other EVM-compatible chains.
Experience integrating wallets such as MetaMask and managing on-chain/off-chain data flows.
Strong debugging skills, attention to detail, and a security-first mindset.
Nice to Have
Experience with smart contract security audits and gas optimization techniques.
Knowledge of Node.js-based backend services or API integration layers.
Previous experience with vesting, staking, or token distribution mechanisms.
Project Scope
This role supports a short-to-mid-term initiative focused on stabilizing and enhancing an existing crypto vesting platform. High-performing developers may have opportunities for ongoing collaboration across additional blockchain and product engineering projects.
Hiring Process
Technical Assessment - Selected candidates will complete a short, clearly scoped technical exercises designed solely to evaluate coding approach and smart contract knowledge.
CTO interview - A final discussion to evaluate technical reasoning, architectural thinking, and team fit. Successful candidates may receive an offer through Contra following this conversation.
Payment in Crypto
Rui Silva
Senior Blockchain Developer - Ethereum/PulseChain - GAM3S.GG
Lisbon, Portugal
Lisbon, Portugal
Full time
Remote
About the Job
We're looking for a Senior Blockchain Developer with strong Ethereum/PulseChain smart contract experience to work on our DeFi/GameFi platform. You'll be building and maintaining betting contracts, yield farming mechanisms, token swap systems, and Web3 frontend integrations for our decentralized application on PulseChain.
Key Responsibilities
Smart Contract Development
System Architecture & Integration
Frontend Web3 Integration
Security & Compliance
Performance & Monitoring
Required Technical Skills
Blockchain Expertise
Frontend Web3 Development
Development Tools
Integration & Tools
We're looking for a Senior Blockchain Developer with strong Ethereum/PulseChain smart contract experience to work on our DeFi/GameFi platform. You'll be building and maintaining betting contracts, yield farming mechanisms, token swap systems, and Web3 frontend integrations for our decentralized application on PulseChain.
Key Responsibilities
Smart Contract Development
System Architecture & Integration
Frontend Web3 Integration
Security & Compliance
Performance & Monitoring
Required Technical Skills
Blockchain Expertise
Frontend Web3 Development
Development Tools
Integration & Tools
Payment in Crypto
Hazel Thomas
Web3 + Supabase Developer Needed to Complete BSC Testnet Waitlist & Staking Platform
Washington, USA
Washington, USA
Part time
Remote
📌 Job Description
We are building a production-ready Web3 waitlist and dashboard platform using Next.js 15 (App Router), BSC Testnet, Supabase, and Wagmi v2.
The core architecture, database schema, and feature roadmap are already defined. We are looking for an experienced developer to complete, polish, and harden the project.
This is not a prototype — the goal is a fully working, deployable system with clean code, security best practices, and proper Web3 UX.
🧩 Project Overview
The platform includes:
Wallet-based user registration (BSC Testnet only)
Automatic network detection & switching
Supabase-backed user management
Automatic virtual card generation (Bronze / Silver / Gold)
Token staking system with transaction logging
Referral system with rewards tracking
Dashboard with analytics & history
X (Twitter) OAuth integration
Discord bot with XP & invite tracking
A detailed README and database schema are already prepared.
✅ Responsibilities
You will be responsible for:
Completing and stabilizing the Next.js App Router implementation
Finalizing wallet connection & network enforcement (Chain ID 97)
Ensuring Supabase RLS policies are correct and secure
Implementing or completing:
Staking flows (stake, unstake, claim, emergency withdraw)
Referral tracking & reward logic
Dashboard analytics & transaction history
Finalizing X (Twitter) OAuth integration
Reviewing and improving overall code quality & structure
Fixing bugs, edge cases, and UX issues
Preparing the app for Railway deployment
(Bonus) Improving performance and Web3 UX
🛠 Tech Stack (Must-Have Experience)
Required:
Next.js 14/15 (App Router)
TypeScript
Wagmi v2 + WalletConnect
EVM chains (BSC preferred)
Supabase (Postgres, RLS, triggers, SQL functions)
Tailwind CSS
Web3 transaction handling & logging
Nice to Have:
Discord bot development (Node.js)
OAuth 2.0 (X / Twitter)
Smart contract interaction (staking contracts)
Framer Motion
shadcn/ui / Radix UI
🔒 Security Expectations
You must be comfortable with:
Wallet validation & chain enforcement
Preventing self-referrals & abuse
Transaction hash uniqueness checks
Secure handling of OAuth tokens
Supabase RLS & role-based access
📦 Deliverables
Fully working, deployable application
Clean, documented codebase
Verified Supabase schema & policies
Functional staking & referral systems
Deployment-ready build (Railway)
Basic handover documentation
⏳ Timeline
Estimated duration: 2–4 months
Start: Immediately
Potential for long-term collaboration
💰 Budget
Open to fixed-price or hourly
Please include:
Your estimated timeline
Relevant Web3 / Next.js projects
Any questions or suggestions to improve the system
🧠 How to Apply
When applying, please answer:
Have you built production Web3 apps with Next.js + Wagmi before?
Have you worked with Supabase RLS & SQL triggers?
Share 1–3 relevant projects (GitHub or live links)
What risks or improvements do you see in this architecture?
Generic proposals will be ignored.
We are building a production-ready Web3 waitlist and dashboard platform using Next.js 15 (App Router), BSC Testnet, Supabase, and Wagmi v2.
The core architecture, database schema, and feature roadmap are already defined. We are looking for an experienced developer to complete, polish, and harden the project.
This is not a prototype — the goal is a fully working, deployable system with clean code, security best practices, and proper Web3 UX.
🧩 Project Overview
The platform includes:
Wallet-based user registration (BSC Testnet only)
Automatic network detection & switching
Supabase-backed user management
Automatic virtual card generation (Bronze / Silver / Gold)
Token staking system with transaction logging
Referral system with rewards tracking
Dashboard with analytics & history
X (Twitter) OAuth integration
Discord bot with XP & invite tracking
A detailed README and database schema are already prepared.
✅ Responsibilities
You will be responsible for:
Completing and stabilizing the Next.js App Router implementation
Finalizing wallet connection & network enforcement (Chain ID 97)
Ensuring Supabase RLS policies are correct and secure
Implementing or completing:
Staking flows (stake, unstake, claim, emergency withdraw)
Referral tracking & reward logic
Dashboard analytics & transaction history
Finalizing X (Twitter) OAuth integration
Reviewing and improving overall code quality & structure
Fixing bugs, edge cases, and UX issues
Preparing the app for Railway deployment
(Bonus) Improving performance and Web3 UX
🛠 Tech Stack (Must-Have Experience)
Required:
Next.js 14/15 (App Router)
TypeScript
Wagmi v2 + WalletConnect
EVM chains (BSC preferred)
Supabase (Postgres, RLS, triggers, SQL functions)
Tailwind CSS
Web3 transaction handling & logging
Nice to Have:
Discord bot development (Node.js)
OAuth 2.0 (X / Twitter)
Smart contract interaction (staking contracts)
Framer Motion
shadcn/ui / Radix UI
🔒 Security Expectations
You must be comfortable with:
Wallet validation & chain enforcement
Preventing self-referrals & abuse
Transaction hash uniqueness checks
Secure handling of OAuth tokens
Supabase RLS & role-based access
📦 Deliverables
Fully working, deployable application
Clean, documented codebase
Verified Supabase schema & policies
Functional staking & referral systems
Deployment-ready build (Railway)
Basic handover documentation
⏳ Timeline
Estimated duration: 2–4 months
Start: Immediately
Potential for long-term collaboration
💰 Budget
Open to fixed-price or hourly
Please include:
Your estimated timeline
Relevant Web3 / Next.js projects
Any questions or suggestions to improve the system
🧠 How to Apply
When applying, please answer:
Have you built production Web3 apps with Next.js + Wagmi before?
Have you worked with Supabase RLS & SQL triggers?
Share 1–3 relevant projects (GitHub or live links)
What risks or improvements do you see in this architecture?
Generic proposals will be ignored.
Payment in Crypto
lucas martin
Senior Web3 / Crypto Trading Platform Developer
Full time
Remote
PumaPulse is launching a new standalone domain focused on building professional-grade crypto trading platforms and on-chain trading tools. We are seeking an experienced freelance Web3 developer to help design, build, and evolve a scalable trading product with commercialization potential.ResponsibilitiesDevelop crypto trading tools, bots, or SaaS platformsIntegrate with DEXs and on-chain protocols (e.g., Solana, Ethereum)Implement real-time blockchain data monitoring and trade executionEnsure security, performance, and MEV-aware designCollaborate on product roadmap, strategy, and future featuresRequirementsStrong experience in Web3 and DeFi developmentProven work with crypto trading bots or on-chain trading systemsExperience with at least one major blockchain ecosystemSolid understanding of smart contract interaction and security best practicesAbility to deliver production-ready code and communicate clearlyNice to HaveExperience productizing tools into SaaS platformsBackground in advanced trading strategies or MEVPrior work with VC-backed or early-stage Web3 projectsEngagementFreelance / contract roleCompetitive compensation based on experiencePotential for long-term collaborationApply with relevant Web3 projects, GitHub links, and availability.
Payment in Crypto
Austin Smart
Fullstack Developer Needed for Web3 Prediction Market Platform
Brooklyn, USA
Brooklyn, USA
Full time
Remote
Summary
We're looking for an experienced Blockchain / Full-Stack Developer to help build a production-ready MVP for a Web3 prediction marketplace.
We’ve already built a basic UI prototype using vibe coding. The goal now is to turn this prototype into a functional, scalable dApp with clean architecture and solid Web3 fundamentals.
This is not a tutorial or experimental project — We’re looking for someone who has real experience shipping blockchain/web3 products.
What You’ll Do
Review and improve an existing UI prototype
Build smart contract logic for a prediction marketplace MVP
Integrate blockchain functionality with the frontend
Develop backend / API logic as needed
Ensure clean, maintainable, production-ready code
Collaborate on product decisions and MVP scope
Tech Stack (Preferred)
Frontend: Next.js / React
Backend: Node.js
Blockchain: Solidity / Rust
Experience with non-EVM chains is a plus (open to discussion)
What We're Looking For
- Strong experience in Blockchain & Web3 development
- Proven ability to build production-ready dApps
- Proficiency in Next.js, React, and Node.js
- Experience designing and shipping MVPs
- Good communication and ability to work independently
Nice to Have
- Previous work on prediction markets, DeFi, or marketplaces
- Experience taking projects from prototype to launch
- Performance, security, and scalability mindset
How to Apply
Please include:
- A brief summary of your Web3 experience
- Links to previous dApps or blockchain projects
- Your preferred tech stack and availability
If you’re an expert in blockchain and Web3 and enjoy building real products from early prototypes, We’d love to hear from you.
We're looking for an experienced Blockchain / Full-Stack Developer to help build a production-ready MVP for a Web3 prediction marketplace.
We’ve already built a basic UI prototype using vibe coding. The goal now is to turn this prototype into a functional, scalable dApp with clean architecture and solid Web3 fundamentals.
This is not a tutorial or experimental project — We’re looking for someone who has real experience shipping blockchain/web3 products.
What You’ll Do
Review and improve an existing UI prototype
Build smart contract logic for a prediction marketplace MVP
Integrate blockchain functionality with the frontend
Develop backend / API logic as needed
Ensure clean, maintainable, production-ready code
Collaborate on product decisions and MVP scope
Tech Stack (Preferred)
Frontend: Next.js / React
Backend: Node.js
Blockchain: Solidity / Rust
Experience with non-EVM chains is a plus (open to discussion)
What We're Looking For
- Strong experience in Blockchain & Web3 development
- Proven ability to build production-ready dApps
- Proficiency in Next.js, React, and Node.js
- Experience designing and shipping MVPs
- Good communication and ability to work independently
Nice to Have
- Previous work on prediction markets, DeFi, or marketplaces
- Experience taking projects from prototype to launch
- Performance, security, and scalability mindset
How to Apply
Please include:
- A brief summary of your Web3 experience
- Links to previous dApps or blockchain projects
- Your preferred tech stack and availability
If you’re an expert in blockchain and Web3 and enjoy building real products from early prototypes, We’d love to hear from you.
Payment in Crypto