LLM Applications Engineer

Uncountable is hiring an LLM Applications Engineer in New York and London. It pays $125k-$160k a year and Level rates it ; you can apply on Uncountable.

Level's read on this job

On Level's scale, this role is Builds AI ●●●●: the job is building AI systems.
Some of the work can be done remotely, according to the posting.
The posting mentions LangChain, LlamaIndex and Haystack among its tools and skills.
Level classes it as a mid-level role.
Uncountable has 32 other open roles on Level.

AI in this role

LangChainLlamaIndexHaystack

ai-agentsai-evaluation

Thank you for your interest in Uncountable Engineering!

Description

Uncountable is seeking experienced engineers to lead the transformation of our platform into an AI-first R&D ecosystem. We are building the next generation of tools that empower scientists at Fortune 500 companies to accelerate discovery through Generative AI.

As an LLM Applications Engineer, you will be the architect of our LLM infrastructure. You won't just be building interfaces; you will be designing the retrieval systems, agentic workflows, and data pipelines that bridge the gap between complex experimental data and actionable AI insights. Your work will directly modernize how the world’s leading researchers interact with their data.

Primary Responsibility

Your primary responsibility is to design, build, and scale the LLM infrastructure and user-facing AI features of the Uncountable Web Platform. This is a hybrid role requiring a deep understanding of full-stack development and the unique challenges of deploying LLMs in production.

Feature Development: Build intuitive, AI-driven UI components that allow scientists to query, analyze, and visualize complex experimental datasets.
Integration: Connect LLM capabilities with our core SQL databases and data analysis engines to ensure high-fidelity, grounded AI responses.

Salary Range: $125K–$160K + Equity

Requirements

2+ years of software development experience with a focus on full-stack web applications.
Proven experience with LLM orchestration frameworks (e.g., LangChain, LlamaIndex, or Haystack).
Proficiency in Python and JavaScript/TypeScript: Ability to work across the AI backend and the React frontend.
Solid Engineering Fundamentals: Experience with API design, asynchronous processing, and performance optimization.

Preferred Qualifications

B.S. in Computer Science or a related technical field.
Experience with LLM Evaluation: Knowledge of how to measure and mitigate "hallucinations" in a scientific/technical context.
Familiarity with SQL: Specifically optimizing queries that serve as the context for LLM prompts.
Product Mindset: A passion for creating "LLM-first" user experiences that feel seamless rather than bolted-on.

Our Current Stack

Backend: Flask (Python), Postgres
Frontend: React (Typescript), Redux, Sass

Benefits

Competitive Salary and Equity
Health and Dental Insurance
401K with Employer Contribution

Agentic Coding

Development at Uncountable has changed dramatically due to the introduction of LLM's. Read more about our practices at:

https://engineering.uncountable.com/coding

We're excited for you to build the future of development with us.

What's next? Learn more about Interviewing at Uncountable

Learn more about our engineering team: Check out our blog

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How we rate this

LLM Applications Engineer at Uncountable rates 91 out of 100 for how much of the daily work is AI. That makes it Builds AI (AI Level 4 of 4). The level is about AI in the job, not seniority.

Classification

Builds AI. The job is building AI systems.

●●●● Builds AI80 to 100
●●●○ Works on AI60 to 79
●●○○ Uses AI40 to 59
●○○○ Little AI0 to 39

Levels come from how often the tools, models and workflows of the role are named in the posting itself. Read the description and count the AI tools, models and workflows it names.

Key facts

LLM Applications Engineer is an open job at Uncountable.
Level rates this role AI Level 4 of 4: Builds AI.
The listed salary is $125k-$160k a year.
The role is based in New York, San Francisco, Munich or London and is marked remote.
The job was posted on January 19, 2026.
Seniority: mid.
Applications are handled by Uncountable. Apply on Uncountable

Prepare for this job

Built from this posting and from similar jobs on Level.

Skills and AI tools this role asks for

AI agentsAI EvaluationLangChainLlamaIndexHaystack

Questions you could be asked

How do you decide when an AI agent can act on its own versus asking for approval first?
How do you decide that one model's output is better than another's for a given task?
What are the limits of LangChain that you've run into, and how did you work around them?
What's a project where you used LlamaIndex hands-on?
Walk me through how you've used Haystack in your day-to-day work.

Adapt your resume

List these exact terms on your resume: AI agents, AI Evaluation, LangChain, LlamaIndex, and Haystack. An applicant tracking system matches the wording, not the idea.
Attach one line of real, concrete experience to at least one of them. A tool named with nothing behind it rarely survives a human read.
Lead with what you built, trained or shipped. This role is judged on the AI system itself, not the tools around it.

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