Senior Product Engineer (AI)

Plain; Remote; GBP 100,000 - 125,000; Full time

Job summary

A leading tech startup in London seeks a Senior Product Engineer to develop cutting-edge AI features for their platform. The ideal candidate will possess strong backend engineering skills and experience with AI product development. Responsibilities include owning AI projects, designing backend services, and driving system scalability. The company offers competitive salaries, equity options, and a flexible work culture.

Benefits

Competitive globalized salaries

Generous option grant

$1000 per year for WFH setup

Flexible, parent-friendly culture

35 days off including public holidays

Qualifications

• Experience shipping AI products in the OpenAI & Anthropic era.
• Hands-on experience with LLM orchestration and API optimization.
• Clear understanding of what makes a great AI product.

Responsibilities

• Own and ship AI features such as agents, assistants, insights.
• Design and implement backend services for AI integrations.
• Drive system scalability through caching and processing patterns.

Skills

AI product engineering

Backend engineering

LLM orchestration

RAG architectures

AI observability

Tools

Postgres

Job description

Your application will be reviewed by us. We'll get back to you within a week. We can't wait to meet you!

Co-Founder & CEO

CO-FOUNDER & CTO

Plain is redefining customer support for the next generation of B2B companies. We’re building the fastest, most powerful platform to help companies move beyond reactive support and build true customer relationships.

Some of the world’s most forward-thinking companies - like Cursor, Raycast, and Granola - trust Plain to unify all customer interactions, enable faster team collaboration, and supercharge their workflows with AI.

B2B customer support is undergoing a seismic shift. AI is transforming the way companies engage with customers, shifting support from a siloed function to a company-wide effort across Slack, Discord, and any other channel you talk to customers in. The old way - slow, manual, and disconnected - no longer works.

What you'll do

We’re in a rare spot. Plain is already powering support for high-growth companies with a lightning-fast, deeply scalable platform. AI has been part of our DNA from the start. Now we’re doubling down to define how it shapes every layer of modern customer support.

This is where you come in.

We're looking for a customer obsessed Senior Product Engineer to help take our AI ambitions to the next level. You’ll build the Infrastructure that helps us build AI features quickly, safely and with confidence. You’ll own problems end to end, and play a key role in building a category-defining product.

In this role, you will:

Own and ship AI features such as our agents, assistants, insights and more - from concept to production.

Design and implement backend services for AI integrations and data pipeline.

Build robust APIs and abstractions for internal AI usage

Drive system scalability: caching, optimization, processing patterns, etc

Contribute and drive the evolution of the infrastructure for AI including architecture, evaluation and iteration pipelines.

Solve complex AI challenges around AI accuracy, reliability, and quality – using rigorous quantitive approaches.

Advocate for our work externally – writing, speaking, and engaging with the broader AI community.

This is a great fit if you…

Are an experienced backend engineer who’s shipped AI products in the OpenAI & Anthropic era – especially text and data-heavy AI applications.

Have hands-on experience with LLM orchestration and LLM API optimization (costs, latency, etc)

Are familiar with RAG architectures and technologies

Have AI observability experience. AI isn’t just about shipping features that sound great – it’s about knowing, conclusively, if they’re making things better.

Have a clear perspective on what makes a great AI product. We want to apply AI with precision, nuance, and real impact – not as a gimmick.

Are product minded and customer focused in how you build software.

Measure your success by user impact, not just technical elegance.

Are self-driven, impact-focused, and thrive in a fast-moving, high-ownership environment.

Bonus: you have experience with agent frameworks and design.

This won't be the right role if you…

Have primarily academic or research ML/AI experience. This role’s looking for someone with Applied AI experience.

Think AI for support is just chatbots and deflection. B2B support is complex – we want AI through the platform, not just automating conversations.

Struggle with ambiguity. We’re an early-stage startup. Things change quickly, and often, knowing what to work on is as important as the work itself.

Prioritize working with the latest tech for its own sake. We choose tools that make us productive – not what’s trendy. (Postgres is great.)

Are looking for a management role. This is a hands-on individual contributor position.

Want the perks of a big company. We offer competitive compensation for our stage, but we’re a startup – this is a different kind of opportunity.

Competitive, globalized salaries for everyone, regardless of where you live

Generous option grant on

employee-friendly terms

Quarterly offsites with the whole company in interesting and fun places

$1000 per year to spend on

your WFH setup

Desks at coworking spaces

whenever you need

Flexible, parent-friendly culture

Enhanced parental leave

35 days, including public holidays,

to take as you wish

At the end of the year, the founders cook the whole team dinner. You might feel that’s a threat rather than a benefit, but we were told in a non-anonymous survey that our food is one of a kind.