Full‑Stack Engineer (Backend‑Focused)
Brazil
Full time
Remote
Compensation is not specified
Role
Full-Stack Engineer
Description
About Ubiminds
Ubiminds is a GPTW‑certified, people‑first company that partners with American software product companies to scale their development footprint. We custom‑curate Brazil’s top 5% talent to support LATAM strategies through staff augmentation and employer‑of‑record services.
We are supporting an HR Tech product company that is building an AI‑powered interview platform, designed to conduct intelligent interviews through natural conversation, real‑time analysis, and automated report generation.
About the Role
We are seeking a Full‑Stack Engineer with strong backend focus to aid in the construction and expansion of an AI‑driven interview platform. You will play a crucial role in a small and growing engineering team, with significant ownership of features and involvement in architectural and technical decisions.
Responsibilities
Backend Development (70%)
- Develop and deploy RESTful APIs using Python and FastAPI.
- Construct scalable backend services with clear separation of concerns.
- Integrate AI services through APIs like GPT‑5 and Whisper, utilizing prompt engineering and structured outputs.
- Manage background jobs and asynchronous processing.
- Facilitate real‑time communication via technologies such as WebSockets and WebRTC.
- Collaborate on database architecture, schema design, and migrations using PostgreSQL.
- Optimize database performance through efficient query writing and maintenance.
- Implement caching and session management with Redis.
- Maintain data consistency in a multi‑tenant SaaS setting.
- Work on infrastructure components like AWS ECS, Lambda, RDS, and S3.
Frontend Development (30%)
- Connect backend APIs to frontend components built with React.
- Create and maintain various frontend elements including forms, tables, dashboards, and data visualizations.
- Address frontend issues resulting from backend modifications.
- Enhance user experience through loading states, validations, and error handling improvements.
Tech Stack
Backend (Primary Focus)
- Languages & Frameworks: Python 3.11+, FastAPI, SQLAlchemy, Pydantic.
- Data: PostgreSQL, Redis, Alembic.
- AI & Integrations: OpenAI API (GPT‑5, Whisper).
- Real‑Time: WebSockets, WebRTC.
Frontend (Supporting Role)
- React 19, Next.js 16, TypeScript.
- Styling: TailwindCSS, Bootstrap Icons.
- State Management: React Context API, React Hook Form.
- Additional Tools: TipTap (rich text editor).
Infrastructure & DevOps
- Amazon Web Services (ECS Fargate, Lambda, RDS, S3).
- Tools: Docker, Terraform.
- Monitoring: CloudWatch, Sentry.
Required Qualifications
Technical Skills (Must‑Have)
- 5+ years of professional experience with Python.
- Proficiency in FastAPI, Flask, or Django.
- Advanced knowledge of PostgreSQL, including optimization and migrations.
- Experience with ORMs, preferably SQLAlchemy.
- Solid understanding of REST API design principles.
- Previous work with third‑party APIs and webhooks.
- Familiarity with async/await and background processing.
- Competence in Git and version control.
- Basic proficiency in React and TypeScript.
Soft Skills
- Effective communication skills in Portuguese (English for reading and writing).
- Strong problem‑solving abilities and attention to detail.
- Comfort in dynamic startup environments.
- Strong sense of ownership and accountability.
Nice to Have
- Familiarity with AI/LLM integrations or prompt engineering.
- Background in NLP or conversational AI.
- Knowledge of Docker and Infrastructure as Code (Terraform).
- Exposure to CI/CD pipelines.
- Experience with microservices, event‑driven architecture, or real‑time systems.
- Previous involvement in startups or HR Tech.
What We Offer
- High technical autonomy and ownership.
- Utilization of modern technologies including AI and real‑time systems.
- Direct input on a tangible product serving real users.
- Agile team dynamics with effective decision‑making processes.
- Opportunities for continuous learning and professional growth.
Skills Required
Ubiminds
Website
Not specified
Company 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