Senior Software Engineer - Python

CSL Group; Watford; On-site; GBP 65,000 - 90,000; Full time

Job summary

CSL Group is seeking a Senior Software Engineer to own software design and delivery for complex, large-scale systems. You will implement code, ensure test coverage, and operate reliable software and tools within CSL's Signalling Engineering domain.

You will lead technical guidance, collaborate with peers and stakeholders, and contribute to a culture of high coding standards while driving efficient, scalable solutions across the product lifecycle.

Qualifications

• Experienced in designing and building reliable software for large-scale applications in complex environments.
• Proficient with popular programming frameworks, development tools, databases and deployment processes.
• Able to guide others, working with stakeholders outside of their immediate team such as Product Owners/Managers, and influencing key decisions.

Responsibilities

• Collaborate with Heads of Engineering and Principal Engineers to shape, document, and enhance best practices and technology standards.
• Provide technical knowledge, insight, and guidance to other engineers as required; review and give feedback on peers' code.
• Support product and other stakeholders in shaping the Product roadmap.
• Maintain complete, accurate and reliable technical documentation.
• Lead troubleshooting and resolution of issues throughout the product life cycle, including out-of-hours incident support.
• Ensure unit testing is implemented alongside their code and is fit for purpose.
• Investigate and evaluate technologies that could provide future benefit to CSL through research and experimentation.

Skills

Software design

Large-scale apps

Programming frameworks

Databases

Test-driven development

QA methodologies

Deployment processes

Stakeholder communication

Job description

• We are a leading international IoT service provider specialising in sectors including Fire, Security, Telecare, Critical National Infrastructure, Retail and Water Utilities.
• We are a rapidly growing, private equity-backed company with operations in multiple countries, including the UK, Ireland, the Nordics, Benelux, and Spain.
• We have completed 6 acquisitions in 6 years, each one adding further expertise and scale to our market-leading propositions.
• We now have over 250 employees within the Group – and this is growing all the time.
• Our high performing team of experts is renowned for delivering leading solutions and services, backed up by worldclass customer support across markets that demand nothing less than absolute certainty.
• Our products and solutions have won over 20 awards across a range of industries.
• We are in the Top 10 Best Places to Work in the UK 2025.
• Whether you’re looking for a new start or looking for a move into a company where you can make a difference, CSL could be the platform you are looking for.

Who Are CSL Looking For?

To be a successful Senior Software Engineer, you must have strong technical expertise and problem-solving skills, capable of tackling complex development backlog tickets with confidence. You are expected to take ownership of backlog tasks, delivering high-quality implementations that align with coding standards, business objectives, and project timelines. Comfortable collaborating with peers and supporting other colleagues, you ensure that solutions are efficient, scalable, and maintainable, contributing to the overall success of the Signalling Engineering team.

The Role:

Software Engineers are responsible for engineering all of the systems, products and services that power CSL.

This means being responsible for the software design, code implementation, test coverage and operation of effective software and supporting toolsets within specific business and technology domains.

The role holder spends their time Exploring, Investigating, Developing, Enhancing and sometimes Decommissioning our provided Tools, Product and Services all with the aim of delivering the backlog, roadmap and overall corporate strategy with their success being measured by outcome value achieved and alignment to the agreed priorities.

This involves translating requirements into quality (meet required metrics) technical solutions then creating code for products and services adhering to our engineering standards that’s maintainable, supportable and with minimal risk to operate and able to be deployed safely into a production environment for use by customers and colleagues.

The Senior Software Engineer is a trusted expert within their Centre of Excellence (domain) for complex implementations, providing technical solutions and guidance. A Senior Engineer is expected to resolve challenging problems efficiently, leveraging their deep understanding of the design, topology, and methodology of their domain.

They play a key role in ensuring successful outcomes through collaboration and technical capability.

Key to being successful is being responsible for creating a diverse, inclusive, and welcoming environment. It is essential to ensure that everyone feels supported to be their authentic self, can grow, develop, and positively contribute to

Key Responsibilities:

People

• Able to work in close partnership with and under the guidance of others – Heads of Engineering, Solution Architect, Technical Programme Manager, Engineering Leads and Principal Engineers.
• Provide technical knowledge, insight, and guidance to other engineers as required.
• Review and give constructive feedback on others’ code through peer review processes.
• Support product and other stakeholders as required in shaping the Product roadmap.
• Be knowledgeable on their domain (Centre of Excellence) they are part of and its place alongside other domains and therefore are comfortable when others consult with them.
• Work with Principals and Engineering Leads in the broader Signalling engineering Team to shape, document, and enhance the best practices and technology standards.

Process

• Effectively participate in the team’s software development methodologies, such as pairing, code and documentation reviewing, testing, and continuous delivery.
• Work with project, product, and technical leads to design software and create implementable specifications and tasks at product and roadmap level.
• Ensure that the team’s technical documentation is always complete, accurate, and reliable.
• Provide frequent and accurate updates on ticket progress, expected timelines, work level outstanding, dependencies, risks, issues and duration spent to Delivery Programme Managers.
• Lead troubleshooting and resolution of issues throughout the product life cycle, including providing out-of-hours support for incident resolution and actively contribute within retrospectives.
• Ensure unit testing is always implemented alongside their code and is always fit for purpose.
• Investigate and evaluate technologies that could provide future benefit to CSL through research and experimentation.

Technology

• Comfortable and dependable in the design and development of effective software that meets complex, strategic business needs for the immediate roadmap and helps to achieve broader CSL objectives.
• Ensures their approaches, code, documentation and testing is aligned to Technology Standards and Practices.
• Ensure the code delivers works as expected (aligned to Acceptance Criteria and Definition of Done), meets wider specifications, reliability, cost efficiency and performance goals.
• Ensures the product and services is integrated with monitoring and support tooling aligned to its operating environment.

Ideal Experience and Knowledge Sought:

• Skilled in designing and building reliable software for large-scale applications in complex environments.
• Experienced in popular programming frameworks, development tools, databases, and deployment processes.
• Capable and comfortable in guiding others, working with stakeholders outside of their immediate team such as Product Owners/Managers, and influencing key decisions – including communicating concerns or issues.
• Demonstratable experience and committed to high coding standards, including being a recognised practitioner of test-driven development and software quality assurance methodologies.
• Previous experience and understanding of what it takes to ensure product changes succeed, through applying best design practices, and by keeping up with new technologies.

The above should not be viewed as an exhaustive list of skills and/or qualifications but rather CSLs view on the ideal candidate.

CSL operates as an equal opportunities employer and we welcome all applications regardless of gender, race, disability, sexual orientation, religion or belief, age, gender reassignment, marital or civil partnership status, pregnancy or maternity.