Backend Engineer, AI (Agent Systems)

ActAI; Greater London; On-site; GBP 60,000 - 90,000; Full time

Job summary

ActAI is seeking a Backend Engineer, AI, to own the inference and orchestration layer powering every AI interaction in our product. You will build and operate production systems that turn model capability into fast, stable APIs used across mobile and desktop clients.

You will design inference pipelines and service boundaries, own monitoring, logging and incident response, and optimize latency and throughput.

Qualifications

• Experience building production AI-powered services.
• Familiar with inference patterns (LLMs, embeddings).
• Strong debugging and observability skills.

Responsibilities

• Build and operate production APIs.
• Design inference pipelines and service boundaries.
• Own monitoring, logging and incident response.
• Optimize latency and throughput.

Skills

Backend engineering

Latency optimization

Production systems

Collaborative team

Tools

Python

NodeJs

Pytorch

OpenAI

Anthropic

SQL

NoSQL

Docker

Job description

There are over 5 billion users using basic applications today such email, notes, tasks, calendar and they're not AI-native. Our mission is to build proactive applications for anyone in the world, who are not used to complex prompting. We aim to bring intelligence to conversations, errands, organising and workflows, with minimal to no prompting.

Our first application is an agent-first mobile communication app. We believe building applications that users use daily for communication, coordination and collaboration needs will help integrate AI into their lives. The net effect is to eliminate misinformation, achieve low coordination costs, enable high quality tasks and collaboration at scale with minimal or little prompting.

Role

As a Backend Engineer, AI, you own the inference and orchestration layer that powers every AI interaction in the product. Your work sits between models and users, where latency, correctness, reliability, and cost directly impact real-world experience.

You will build and operate production systems that turn model capability into fast, stable, observable APIs used across mobile and desktop clients.

Focus

• Build and operate backend systems that serve AI-powered features in production.
• Design inference pipelines, orchestration layers, and service boundaries around models.
• Own production concerns: monitoring, logging, alerting, and incident response.
• Optimize latency and throughput across inference, caching, batching, and streaming.

Ideal Experiences

• Experience running high-throughput, low-latency services.
• Familiarity with AI inference patterns (LLMs, embeddings, multimodal).
• Bias toward shipping and learning from production behavior.

Outcomes

• Backend systems run reliably at scale, handling production AI traffic with low latency and high throughput.
• APIs are stable, clear, and support seamless integration with frontend and ML systems.
• Production incidents are quickly detected, diagnosed, and resolved, minimizing user impact.
• Iterative improvements based on real usage continuously increase system performance and reliability.
• Python
• NodeJs
• Pytorch
• OpenAI / Anthropic / open-source LLMs
• SQL & noSQL
• Docker

How We Work

The best products today in the world were built by small, world class teams. We are a high talent density and hands-on team. We make decisions collectively, move at rapid speed, striking a balance between shipping high quality work and learning. Joining our team requires the ability to bring structure, exercise judgment, and execute independently. Our goal is to put in hands of our users a truly magical product