Backend Engineer, AI Systems

ActAI; Greater London; Hybrid; GBP 90,000 - 140,000; Full time

Job summary

ActAI is seeking a Backend Engineer to own the inference and orchestration layer powering AI interactions across our product. You will design and run production-grade services with low latency and high reliability for mobile and desktop clients.

As part of the role, you will build multi-step AI workflows, implement routing, caching, batching, streaming, and state management, and collaborate with ML teams to translate model capabilities into stable APIs and reliable systems.

Qualifications

• Experience operating high-throughput, low-latency services.
• Familiarity with AI inference patterns (LLMs, embeddings).
• Shipping-focused with strong reliability in production.

Responsibilities

• Build and operate backend systems serving AI-powered features in production.
• Design inference pipelines and orchestration for multi-step workflows.
• Manage routing, caching, batching, streaming, and state of AI requests.
• Optimize latency, throughput, and cost for model inference.
• Implement observability with logging, tracing, and debugging.
• Collaborate with ML and product teams to deliver stable APIs.

Skills

High throughput

Low latency

AI inference

Observability

Production systems

LLMs

Tools

Python

Node.js

PyTorch

Docker

OpenAI API

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 prompting.

Our product focuses on achieving high reliability for long-running workflows, persistent context, and real-world task completion. We believe products will greatly reduce hallucinations

Our objective is to organise anyone's life, allowing us all to spend time on valuable and meaningful things

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. 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 and orchestration layers that handle multi-step workflows, tool calls, and retries
• Manage the full lifecycle of AI requests: routing, caching, batching, streaming, and state management
• Optimize latency, throughput, and cost across model inference and downstream systems
• Design systems that remain reliable despite non-deterministic model behavior and external dependencies
• Implement observability for AI systems, including logging, tracing, and debugging of model outputs and failures
• Collaborate with ML and product teams to translate model capabilities into stable, production-grade APIs

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.
• Multi-step AI workflows complete successfully across tools and services, with robust handling of failures and retries
• 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.
• System design evolves to support increasing scale, complexity, and new AI capabilities without major rewrites.
• 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