Lead Backend Engineer

About ZYSYGY

ZYSYGY is building Germany's zero-fee payment network. Merchants pay zero transaction fees. We route payments directly over SEPA Instant, bypassing Visa, Mastercard, and the entire card network chain. No hardware. No card reader. Just a phone.

We are building the first company to combine a fully software-based merchant POS with a consumer super-app for everyday financial life: payments, transport, utilities, government services, all in one place. Think what UPI did for India. We are doing it for Germany, from the ground up, on banking rails.

Role Overview

You will join the core engineering team as a founding engineer. You will own the backend payment engine end to end: transaction flows, wallet management, SEPA Instant settlement, KYB/KYC integration, recurring mandates, refund logic, and the compliance export layer (DATEV, Kassenbuch, GoBD, fiskaltrust). On mobile, you will contribute to the React Native consumer and merchant apps alongside our mobile engineer.

You will own what you build from development through deployment, monitoring, and production reliability. The architecture decisions you make in the first six months will run in production for years.

What you will do

Design and build the backend payment engine: transaction flows, wallet management, SEPA Instant settlement, offline payment authorization, and recurring mandate billing.

Own KYB/KYC integration and the compliance export layer: DATEV, Kassenbuch, GoBD, and fiskaltrust for KassenSichV.

Build REST APIs for financial-grade reliability and high-throughput transaction processing, including full R-transaction handling and reconciliation pipelines.

Contribute to the React Native consumer and merchant mobile apps alongside our mobile engineer.

Own the full lifecycle of what you build, from development through deployment, monitoring, and continuous improvement.

Integrate AI tooling into your development workflow as a matter of course: code generation, automated testing, and intelligent review.

Who you are

Meaningful hands-on experience building payment systems, fintech infrastructure, or financial APIs.

You have designed a ledger. You understand double-entry bookkeeping, immutable transaction records, and why you never update a financial row.

You have solved the partial failure. Money left one wallet and did not arrive in the other. You know how to detect it, resolve it, and make sure it does not happen again.

You understand idempotency at a design level. You have built systems that survive client retries, duplicate webhooks, and network drops without double-charging anyone.

You have built or reasoned about reconciliation: detecting discrepancies between your internal ledger and an external settlement file, and resolving them reliably at scale.

You understand KYC and KYB state machines, what happens when verification status changes mid-transaction, and what a regulator expects from your audit trail.

You are comfortable with SQL databases and own the full lifecycle of your code from development through deployment.

You can communicate technical decisions clearly to non-technical stakeholders. At this stage of the company, that matters.

You are a continuous learner. Payments infrastructure is a deep domain and you treat it that way.

You are comfortable with ambiguity and early-stage risk. There is no playbook yet. You will help write it.

Strong academic background preferred. Demonstrated engineering ability matters more than institution.

Relocation

Relocation to Munich, Germany, is on the table for the right candidate, including visa support.

Connect with the Founder

You can also connect with me on LinkedIn at www.linkedin.com/in/shabbir-maimoon

• Develop, test, and maintain server-side applications using Node.js and related technologies.
• Design and implement RESTful APIs and microservices architecture to support frontend functionality.
• Collaborate with cross-functional teams to understand business needs and translate them into technical solutions.
• Optimize application performance, ensuring scalability and reliability.
• Conduct code reviews, mentor junior developers, and ensure adherence to best practices.
• Stay updated with emerging backend technologies and methodologies to improve development processes.

Mandatory

• SaaS experience of 2 years with total development experience of 4 years
• Must have worked in a smaller company of less than 100
• Should have built solutions/softwares end to end and not just as a part of bigger team
• Should see themselves going deeper into the same role even 5 years down the line
• Should have knowledge on Node.js, MongoDB, and AWS
• Strong understanding of asynchronous programming, event-driven architecture, and Node.js design patterns.
• Proficiency in working with databases such as PostgreSQL, MongoDB, or MySQL.
• Experience with API development, including RESTful services and microservices.
• Familiarity with cloud platforms such as AWS, Azure, or Google Cloud.
• Strong problem-solving skills and the ability to debug complex server-side issues.

Essential

• Proficiency with version control systems like Git.
• Experience with CI/CD pipelines and deployment automation.
• Knowledge of system design and scalable architecture.
• Understanding of security best practices and implementing secure APIs.

Good to Have

• Experience with GraphQL and related backend technologies.
• Knowledge of containerization and orchestration tools like Docker and Kubernetes.
• Familiarity with message brokers like RabbitMQ or Kafka.
• Experience with platforms like Shopify, BigCommerce, or other e-commerce technologies.
• Exposure to frontend technologies such as React for better cross-functional collaboration.

Basic Qualification: 

• Programming experience with at least one modern language such as Java, Node.js  
• Experience with NoSQL databases like MongoDB 
• 2+ years of experience contributing to the architecture and design (architecture, design patterns, reliability and scaling) of new and current systems. 
• Bachelor Degree in Computer Science or related field. 
• Computer Science fundamentals in object-oriented design, data structures, 
• algorithm design, problem solving, and complexity analysis. 

Preferred Qualification: 

• Experience building complex applications on distributed systems that have been successfully deployed for a large customer base. 
• Experience with Agile Scrum, having served as a Scrum Master and delivered results. 
• Application of advanced coding techniques, such as dependency injection. 
• Proven experience with: writing design documents, leading code reviews, 
• applying SCM, managing builds and managing releases. 
• Knowledge of important design patterns 
• Applying unit testing / TDD to reduce testing cycles and production support 
• load. 

Job Description:

Engage in code design, testing, integration, deployment, and enhancements

Write high-quality code and take responsibility for tasks

Solve performance bottlenecks

Communicate and collaborate with product manager, QA, and UI/UX teams

Deliver with quality, on-time in a fast-paced start-up environment

Have a strong sense of code quality

Candidate Profile:

Bachelor’s/Master’s degree in Engineering, Computer Science (or equivalent experience)

At least 5+ years of relevant experience as a back-end engineer

Excellent Java and object-oriented development skills

Experience in building and scaling microservices

Strong problem-solving skills, technical troubleshooting, and diagnosing

Solid knowledge of RDBMS and NoSQL technologies

Experience in developing back-ends for enterprise systems

Knowledge of debugging performance and optimization techniques

Experience in Java, Mongo, MySQL, AWS technologies, ELK stack, Spring boot, Kafka

Good knowledge of cloud technologies eg. AWS

Demonstrated ability to deliver in a fast-paced environment

Job Description:

• Integration of user-facing elements developed by front-end developers.
• Build efficient, testable, and reusable PHP modules.
• Solve complex performance problems and architectural challenges.
• Integration of data storage solutions (may include databases, key-value stores, blob stores, etc.)
• Strong knowledge of PHP web frameworks (such as Laravel, Codeignitor, Yii, etc depending on your technology stack)
• Understanding the fully synchronous behavior of PHP.
• Understanding of MVC design patterns.
• Basic understanding of front-end technologies, such as JavaScript, JQuery, HTML5 and CSS3
• Knowledge of object oriented PHP programming
• Understanding accessibility and security compliance (Depending on the specific project)
• Strong knowledge of the common PHP or web server exploits and their solutions.
• Understanding fundamental design principles behind a scalable application
• User authentication and authorization between multiple systems, servers, and environments
• Integration of multiple data sources and databases into one system
• Familiarity with limitations of PHP as a platform and its workarounds
• Creating database schemas that represent and support business processes
• Familiarity with SQL/NoSQL databases and their declarative query languages
• Proficient understanding of code versioning tools, such as Gif.
• Build efficient, testable, and reusable PHP modules.
• Solve complex performance problems and architectural challenges
• Integration of data storage solutions (may include databases, key-value stores, blob stores, etc}
• Hands on Experience with AWS and NoSQL Database, Integration of AWS Services. (Mandatory)

Development: HTML5, CSS3, JS, JQuery, PHP(Must), Python, Java, Git, Dev Tools, C//.

Development Framework: Laravel, Codeigniter, React JS, Vue JS, Bootstrap. 

Tools: Trello, Slack, ASANA, Visual Studio Code, PHPStorm, Github, Selenium

Technologies Frameworks: Bootstrap, Laravel, WordPress. 

Senior Software Engineer (Python)

Job description

Fulfil’s software engineers develop the next-generation technologies that change how millions of customer orders are fulfilled by merchants. Our products need to handle information at massive scale. We're looking for engineers who bring fresh ideas from all areas into our technology.

As a senior software engineer, you will work on our python based ORM and applications that scales to handle millions of transactions every hour. This is mission critical software and your primary focus will be building robust and scalable solutions that are easy to maintain.

In this role, you will be collaborating closely with the rest of the team working on different layers of infrastructure in an international environment. Therefore, a commitment to collaborative problem solving, sophisticated design, and quality product are important.

What You’ll Do:

• Own definition and implementation of API interfaces (REST and GraphQL). We take pride in our 100% open API with over 600 endpoints.
• Implement simple solutions to complex business logic that enables our merchants to manage financials, orders and shipments across millions of transactions.
• Build reusable components and packages for future use.
• Translate specs and user stories into reviewable, test covered patches.
• Peer review code and refactor existing code.
• Integrate with our eCommerce partners (Shopify, BigCommerce, Amazon), shipping partners (UPS, USPS, FedEx, DHL) and EDI.
• Manage Kubernetes and Docker based global deployment of our infrastructure.

Requirements

We’re Looking for Someone With:

• Experience working with ORMs like SQLAlchemy or Django
• Experience with SQL and databases (Postgres preferred)
• Experience in developing large server side applications and microservices
• Ability to create high quality code
• Experience with python testing tools (pytest) and test automation
• Familiarity with code versioning tools like GIT
• Strong sense of ownership and leadership quality
• Experienced in the tools of our web stack
• Python
• Celery
• Postgres
• Redis
• RabbitMQ

Nice to Haves:

• Prior experience at a growth stage Internet/Software company
• Experience with ReactJS, Google Cloud, Heroku
• Cloud deployment and scaling experience

About Us:

Fulfil.io helps high growth, high volume merchants simplify operations and scale for growth. With the rise in omni-channel commerce, Fulfil was founded with the simple idea that merchant operations need to be simplified in order to deliver amazing retail experiences. Fulfil enables businesses to turn their back office operations into an accelerator for growth by integrating order management, inventory management, warehouse management, vendor/supplier management, wholesale, manufacturing, financials and customer service, into one seamless solution. We believe merchants should love their operations platform, and we work hard to make that happen every single day. Fulfil.io is a trusted solution for brands like EndySleep, Mejuri, Lie-Nielson Toolworks, and many more.  

Fulfil.io is a venture backed technology company with offices in San Francisco, Toronto, and Bangalore. The team is made up of people who want to feel challenged at work, be the best at their craft and learn from one another. We come from different backgrounds and experiences, all passionate about the work we do, the team we do it with, and the customers we do it for. Join us in our journey to simplify operations and empower merchants around the world!  

Are you passionate about using technology to make people's lives better? Are you interested in becoming a part of one of the hottest trends in the world of start-ups today? Are you excited about joining the online ultra-fast grocery delivery service business pioneer and driving the trend forward? Then this may be the right opportunity for you.

Role and Responsibilities

1. Helping lead the software development lifecycle: technical design, implementation, testing, deployment, and support.
2. Working with cross-functional teams effectively to enable business growth.
3. Proactively identifying engineering bottlenecks and initiating proposals to improve them.
4. Writing high-quality, well-tested code in alignment with industry-wide best practices.
5. Applying a product mindset to back-end systems.
6. 1.  

1. About five years of experience delivering product-quality code in an agile set-up
2. Experience with Node.js (Hapi, Restify, Express, Mongoose, Socket.IO, Mocha)
3. Experience with Elasticsearch
4. Experience building and deploying Docker containers
5. Strong general Linux experience
6. Extensive experience with REST APIs
7. Experience with microservice architecture
8. Experience with MongoDB
9. Expert knowledge of Redis and caching strategies
10. Strong knowledge of unit/integration testing, including the art of mocking and writing testable code

1. Passionate about technology and making an impact.
2. A perpetual learner, who stretches their boundaries and enjoys new ideas.
3. A doer who takes initiative and works well in a team.

Blok is a technology-first online ultra-fast grocery delivery service business, and we are on our way to revolutionize how millions of people across countries consume groceries. We believe in a world where getting everything you need, when you need it, sustainably, is the new normal. And it takes less than 10 minutes.

We believe we are positioned to lead this revolution. Why? Our founding and early team have held senior positions at Deliveroo, Uber, Glovo, Mercadona, or Unilever. We have done this before, and we believe we can do it again. But this time, even better.

Embark on the journey and help us launch the revolution in one of the highest growth industries of the year. Help us shape the new normal.