Why Verifone

For more than 40 years Verifone has established a remarkable record of leadership in the electronic payment technology industry. Verifone has one of the leading electronic payment solutions brands and is one of the largest providers of electronic payment systems worldwide.

Verifone has a diverse, dynamic and fast paced work environment in which employees are focused on results and have opportunities to excel. We take pride in the fact that we work with leading retailers, merchants, banks, and third party partners to invent and deliver innovative payments solution around the world. We strive for excellence in our products and services, and are obsessed with customer happiness. Across the globe, Verifone employees are leading the payments industry through experience, innovation, and an ambitious spirit. Whether it’s developing the next platform of secure payment systems or searching for new ways to bring electronic payments to new markets, the team at Verifone is dedicated to the success of our customers, partners and investors. It is this passion for innovation that drives each one of our employees for personal and professional success.

Verifone is proudly an in-office work culture as we see immense benefits to career development and business results from our colleagues being physically co-located.

About The Role

We are seeking a London‑based Senior Software Engineer (Node.js / TypeScript) to build and operate backend services supporting payment, checkout, and transactional workflows. You will collaborate closely with Product, Frontend, Platform, and Infrastructure teams to deliver secure, scalable APIs in high‑throughput environments.

This role sits at the core of Verifone’s payments and checkout platform, where backend engineering directly impacts secure, high‑volume transactions used globally. You’ll design and operate scalable, production‑critical systems that must perform reliably under real‑world load, evolving payment methods, and strict security requirements.

Required Skills and Experience Needed

Programming Languages

• TypeScript (version 3.x or higher)
• Node.js (version 16 or higher)

Backend Frameworks & Libraries

• Backend frameworks such as Hapi.js, or alternatives including Express, Fastify, or NestJS
• Validation using Joi
• Authentication and authorization using JWT and OAuth2

Architecture & Design

• Strong grounding in Clean Architecture and Domain‑Driven Design (DDD)
• Dependency Injection (e.g., InversifyJS)
• Repository and modular design patterns
• Experience building maintainable, testable backend systems

APIs & Data

• Design and operation of RESTful APIs
• API versioning and request validation
• Advanced filtering using RSQL or equivalent
• Experience with MongoDB (modeling, indexing, performance tuning)
• Experience with Redis for caching or messaging
• Database migrations and schema evolution

Cloud & Infrastructure

• Hands‑on experience with AWS services such as EC2, S3, Secrets Manager, and CloudWatch
• Docker and Docker Compose
• Strong discipline with CI/CD pipelines and Git workflows

Testing & Quality

• Automated testing using Jest or Mocha/Chai/Sinon
• End‑to‑end testing with Cypress (optional)
• Strong focus on code quality, reliability, and maintainability

Bonus Skills and Experience

Payments & Security

• Experience integrating payment providers such as Stripe, PayPal, or Klarna
• Knowledge of authorization, capture, and refund flows
• Experience with 3D Secure
• Awareness of PCI‑DSS requirements and security best practices
• Understanding of checkout and transactional domain flows

Production Engineering

• Performance optimization and debugging in production systems
• Exposure to monitoring or APM tools (e.g., AppDynamics or similar)
• Experience operating high‑availability or fault‑tolerant systems
• Familiarity with fraud‑related considerations

Frontend & Platform Exposure

• Experience working alongside frontend frameworks such as Angular or React
• Familiarity with RxJS and state management (NgRx or Redux)
• Server‑side rendering with Pug templates
• HTML/CSS with SASS or PostCSS
• Iframe‑based widget embedding

Additional Bonuses

• Fintech, payments, or e‑commerce domain experience
• Messaging systems such as Kafka, RabbitMQ, or Redis Pub/Sub
• Internationalization (i18n) systems
• Puppeteer for PDF or receipt generation

Our Commitment

Verifone is committed to creating a diverse environment and is proud to be an equal opportunity employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, gender, gender identity or expression, sexual orientation, national origin, genetics, disability, age, or veteran.

We are looking for an engineer with experience in low-level systems programming and optimisation to join our growing ML team. 

Machine learning is a critical pillar of Jane Street's global business. Our ever-evolving trading environment serves as a unique, rapid-feedback platform for ML experimentation, allowing us to incorporate new ideas with relatively little friction.

Your part here is optimising the performance of our models – both training and inference. We care about efficient large-scale training, low-latency inference in real-time systems and high-throughput inference in research. Part of this is improving straightforward CUDA, but the interesting part needs a whole-systems approach, including storage systems, networking and host- and GPU-level considerations. Zooming in, we also want to ensure our platform makes sense even at the lowest level – is all that throughput actually goodput? Does loading that vector from the L2 cache really take that long?

If you’ve never thought about a career in finance, you’re in good company. Many of us were in the same position before working here. If you have a curious mind and a passion for solving interesting problems, we have a feeling you’ll fit right in. 

There’s no fixed set of skills, but here are some of the things we’re looking for:

• An understanding of modern ML techniques and toolsets
• The experience and systems knowledge required to debug a training run’s performance end to end
• Low-level GPU knowledge of PTX, SASS, warps, cooperative groups, Tensor Cores and the memory hierarchy
• Debugging and optimisation experience using tools like CUDA GDB, NSight Systems, NSight Computesight-systems and nsight-compute
• Library knowledge of Triton, CUTLASS, CUB, Thrust, cuDNN and cuBLAS
• Intuition about the latency and throughput characteristics of CUDA graph launch, tensor core arithmetic, warp-level synchronization and asynchronous memory loads
• Background in Infiniband, RoCE, GPUDirect, PXN, rail optimisation and NVLink, and how to use these networking technologies to link up GPU clusters
• An understanding of the collective algorithms supporting distributed GPU training in NCCL or MPI
• An inventive approach and the willingness to ask hard questions about whether we're taking the right approaches and using the right tools
• Fluency in English

If you're a recruiting agency and want to partner with us, please reach out to agency-partnerships@janestreet.com.