Senior Software Engineer in London

We're hiring a Senior Software Engineer to lead implementation across our shared modern stack. This is a hands-on role for someone who owns technical decisions, writes production code, and delivers high-quality systems across multiple PE portfolio products. Avallo partners with private equity firms and their portfolio companies to design, build, and scale software that drives measurable business value.

We work across multiple products and client environments, and many of those projects are built on a shared modern stack. That gives our engineers the opportunity to move quickly, apply patterns repeatedly, and deliver high-quality systems across a range of business contexts. You should be energized by building software from the ground up, improving engineering standards, and working in a fast-moving environment where priorities can shift across projects but the bar for quality stays high.

Our core stack includes TypeScript, Node.js, pnpm, Turborepo, NestJS, Prisma, PostgreSQL, Redis, React, Next.js, Vite, Tailwind CSS, shadcn/ui, TanStack Query, Stripe, Auth0, Sentry, OpenTelemetry, Jest, ESLint, and Prettier. Many of our engagements run on this same foundation, so we are looking for an engineer who can operate confidently within these tools and patterns while helping evolve them over time.

In this role, you will:

• Design and build RESTful and GraphQL APIs using NestJS and Prisma on PostgreSQL
• Develop modern web applications and internal dashboards in Next.js, React, and Vite with Tailwind CSS and shadcn/ui
• Integrate third-party systems including Stripe, Auth0, and other client-specific tools
• Write clean, well-tested TypeScript across frontend and backend codebases
• Establish and improve engineering standards, patterns, and documentation across multiple product environments
• Participate in architectural decisions and technical design reviews
• Work directly with internal teammates and client stakeholders to translate business requirements into robust technical solutions
• Identify and address performance, reliability, and scalability concerns proactively
• Contribute to observability and monitoring practices using Sentry and OpenTelemetry
• Mentor and support other engineers on the team

What we're looking for:

• 5+ years of professional software engineering experience with a focus on TypeScript and full-stack web development
• Strong command of Node.js, NestJS, and Prisma — you've built and shipped production APIs
• Solid experience with React and Next.js — you're comfortable with both the frontend and the framework
• Familiarity with monorepo tooling; pnpm and Turborepo experience is a strong advantage
• Experience integrating authentication systems such as Auth0 or similar
• Comfortable working with PostgreSQL and Redis in production environments
• A track record of writing maintainable, well-tested code and holding a high quality bar under real delivery pressure
• Strong communication skills — you can articulate technical decisions clearly to both engineers and non-engineers
• Able to operate independently, manage your own priorities, and take end-to-end ownership of features

Nice to have:

• Experience working across multiple simultaneous products or client engagements
• Familiarity with Stripe Billing, Connect, or usage-based pricing models
• Exposure to private equity or technology consulting environments
• Experience with TanStack Query, Zod, or similar libraries in our stack
• Understanding of observability patterns using OpenTelemetry
• Prior involvement in establishing engineering standards, onboarding processes, or internal tooling