Principal Software Engineer: Scalable Data & ML Platform

Simple Machines; Greater London; Hybrid; GBP 120,000 - 180,000; Full time

Job summary

Simple Machines, a leading independent boutique technology firm, seeks a Principal Software Engineer in London. This hybrid, full-time role focuses on delivering complex, scalable systems across backend, APIs, frontend, data pipelines, and cloud infrastructure for ambitious clients.

You’ll collaborate with internal teams and client stakeholders to influence technical direction while owning end-to-end design, delivery, and quality through iterative, consultative engineering practices.

Qualifications

• Proven JVM-based development experience with Kotlin preferred and Java welcomed.
• Experience designing and implementing data-driven APIs for scalable systems.
• Background building large-scale web services and reliable data pipelines.
• Strong SQL skills including schema design and performance-aware queries.
• Extensive automated testing experience (unit/integration; TDD/BDD preferred).
• Front-end exposure with React, TypeScript, Redux, and Tailwind.

Responsibilities

• Design and build backend services for a highly scalable platform.
• Own API and infrastructure design for robust applications.
• Document designs and requirements clearly for internal teams and clients.
• Deliver end-to-end solutions: build, automate, deploy and support.
• Collaborate with clients and delivery teams to translate business needs into technical solutions.
• Operate in an Agile, iterative delivery model.
• Work in a hybrid setup with remote and in-person team members and stakeholders.

Skills

Kotlin

Java

APIs design

Large-scale web services

SQL

Testing (TDD/BDD)

React

TypeScript

Redux

Tailwind

AWS

GCP

Azure

Terraform

CloudFormation

Docker

Kubernetes

ECS

Scala (nice to have)

RxJava

Ktor

NoSQL (DynamoDB, Cassandra, BigTable,)

Git workflows

Tools

Docker

Kubernetes

Terraform

CloudFormation

Job description

Simple Machines, a leading independent boutique technology firm, seeks a Principal Software Engineer in London. This hybrid, full-time role focuses on delivering complex, scalable systems across backend, APIs, frontend, data pipelines, and cloud infrastructure for ambitious clients.

You’ll collaborate with internal teams and client stakeholders to influence technical direction while owning end-to-end design, delivery, and quality through iterative, consultative engineering practices.