Principal Software Engineer

Tact; Greater London; Hybrid; GBP 110,000 - 130,000; Full time

Benefits offered by this job

Health insurance

Pension

Learning and development

Hybrid work in London

Job summary

Tact, a London-based fintech, is seeking a Principal Engineer to own architecture and drive delivery for AI, LLM and data products. You’ll stay hands-on, write production code in Node.js and Python, and influence technical direction across a small, focused team.

The role blends finance-domain insight with architecture leadership in a hybrid London setting. Expect to work on greenfield AI features, scale complex systems, and shape product decisions while collaborating with stakeholders.

Qualifications

• Experience in finance or financial services.
• Strong AWS knowledge.
• Architecture and technical leadership experience.
• Experience building AI/LLM functionality into real products.
• Database experience, PostgreSQL; DynamoDB/Elasticsearch are a bonus.

Responsibilities

• Own complex projects from idea to production and shape the architecture.
• Make key technical decisions and write production code.
• Lead engineers through delivery and ensure quality.

Skills

Financial services experience

Technical leadership

AI/LLM integration

Architectural decisions

Tools

Node.js

Python

AWS

PostgreSQL

DynamoDB

Elasticsearch

Job description

Principal Engineer // London hybrid // £120,000

Want to build AI products used by some of the biggest names in global credit markets?

You'll be joining an established financial technology business building specialist data, analytics and AI products for hedge funds, asset managers, investment banks and professional credit investors.

Their technology is already trusted across institutional credit markets, with a platform covering thousands of bond and loan issuers and hundreds of thousands of financial filings. Now they're investing heavily in the next generation of their platform, particularly AI, LLMs and agent-based products.

With an engineering team of around 14, you'll have serious technical influence without getting lost in a huge engineering organisation.

The role

As a Principal Engineer, you'll take ownership of complex projects from idea through to production – shaping the architecture, making key technical decisions, writing production code and leading engineers through delivery.

They need someone who understands finance.

You'll be building technology for sophisticated financial users, so you need to understand the domain, the data and the problems you're solving – and be able to use that knowledge when making technical and product decisions.

You'll be working across Node.js, Python and AWS.

• Designing architecture and making key technical decisions
• Building greenfield AI, LLM and agent-based products
• Writing production code across Node.js and Python
• Working with AWS and Infrastructure as Code
• Designing and developing databases, particularly PostgreSQL
• Using financial domain knowledge to shape technical solutions
• Technically leading engineers through complex projects

This isn't a move away from engineering into management. You'll remain hands-on and close to the code, but with significant ownership over architecture, technical direction and delivery.

What they're looking for:

• Strong experience within finance or financial services
• A genuine understanding of financial products, markets and data
• Strong AWS knowledge
• Architecture and technical leadership experience
• Experience building AI/LLM functionality into real products
• Database experience, ideally PostgreSQL
• DynamoDB and Elasticsearch are a bonus

What's on offer

• Up to £120,000 base salary
• 2 days per week in central London
• Greenfield AI and agent-based projects
• Huge technical and architectural ownership
• 25 days holiday + bank holidays
• Health insurance and pension
• Choice of high-quality tech kit
• Learning and development