Fullstack Software Engineer in London

Location: London, UK

On-Site | Full-time

Compensation: Competitive Compensation

Our client is an early-stage, high-impact, revenue-generating AI startup that is fundamentally redefining business automation. This organization sells completed business outcomes—delivering highly automated, autonomous pipelines that directly close revenue for clients ranging from fast-growing startups to Fortune 500 enterprises.

With strong product-market fit, consistent month-over-month growth, and a clear roadmap, the engineering team is currently scaling up. This is a rare opportunity to join an elite, tight-knit, and highly leveraged engineering team where every line of code directly drives revenue and shapes foundational systems from scratch. The team operates in a fast-paced, high-momentum environment that values intense collaboration. To maintain this high-engagement culture, this role is 100% on-site (five days a week) at the client's office in Piccadilly, London.

• End-to-End System Ownership: Own complex technical problems from scope to deployment, building and iterating on foundational systems from scratch with real users from day one.
• Next-Generation Infrastructure: Build and scale custom calling and dialer infrastructure with autonomous AI agents at the core.
• Autonomous AI Workflows: Develop and optimize high-throughput AI Inbound SDR systems capable of autonomously managing thousands of callbacks and converting them to scheduled meetings.
• Closed-Loop Intelligence: Build post-interaction intelligence layers that generate real-time insights, customized proposals, and targeting signals to feed directly back into campaigns.
• High-Scale Data Pipelines: Engineer advanced prospecting engines featuring custom web scraping, AI-driven qualification pipelines, and highly optimized list-logic systems.
• Stack Optimization: Work within a modern, robust tech stack utilizing TypeScript, React, Next.js, AWS, OpenSearch, Trigger.dev, ClickHouse, and Datadog.

• Top-Tier Tech Experience: Proven software engineering experience at a globally recognized, high-caliber technology organization (e.g., FAANG, Bloomberg, Stripe, Shopify, Revolut, Datadog, or direct equivalent) is strictly required.
• Startup DNA: Prior experience working in a fast-growing startup or highly agile team (<20>
• Professional Tenure: Minimum of 3+ years of professional software engineering experience for mid-level candidates, and 6+ years for senior-level candidates.
• Full-Stack Proficiency: Deep expertise in full-stack web development, with strong production experience in TypeScript and React (Next.js experience is highly preferred).
• CS Fundamentals: Exceptional computer science fundamentals, including data structures, algorithms, and performance trade-offs, backed by a Computer Science degree or equivalent from a top-tier university.
• Architectural Capability: Proven ability to design complete, end-to-end systems from scratch, demonstrating true systems-level thinking rather than simply executing on pre-defined architectures.
• AI & LLM Tooling: Practical experience building with AI/LLMs, autonomous agents, RAG systems, or advanced LLM-powered application features.

• On-Site Presence: Must be currently based in London (or fully willing to relocate) and committed to working on-site five days a week in Piccadilly (no exceptions).

• Competitive Compensation: Market-aligned base salary with highly flexible stock-for-salary trade-off options, structured to reward those who value meaningful equity in a high-growth, revenue-generating startup.
• Visa Sponsorship: Full visa sponsorship is available for qualified international candidates.
• Health & Wellness: Comprehensive private health and dental insurance.
• Retirement: Company-matched pension scheme.
• Office Perks: Fully covered late-night dinners and taxi rides home for team members working past 8:00 PM.

• Stage 1: Screening Call - An introductory conversation to align on professional background, career aspirations, and cultural fit.
• Stage 2: Technical Evaluation Phase - Systems Design Interview: An interactive session focused on mapping a complex, real-world problem statement to a highly scalable, end-to-end architectural solution. Take-Home Assessment: A practical exercise utilizing a provided application scaffold. Candidates will solve a problem using an AI agent and must be prepared to articulate, explain, and defend the agent’s outputs.
• Stage 3: Follow-Up & Culture Fit - A final discussion to meet additional team members, review role expectations, and finalize compensation details.

Due to the high volume of applications we anticipate, we regret that we are unable to provide individual feedback to all candidates. If you do not hear back from us within 4 weeks of your application, please assume that you have not been successful on this occasion. We genuinely appreciate your interest and wish you the best in your job search.

Commitment to Equality and Accessibility: At MLabs, we are committed to offer equal opportunities to all candidates. We ensure no discrimination, accessible job adverts, and providing information in accessible formats. Our goal is to foster a diverse, inclusive workplace with equal opportunities for all. If you need any reasonable adjustments during any part of the hiring process or you would like to see the job-advert in an accessible format please let us know at the earliest opportunity by emailing human-resources@mlabs.city.

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