Staff / Principal Engineer

A Staff Engineer is a software engineering expert who takes on complex technical problems and helps other engineers move their projects forward. A Principal Engineer helps solve these problems across several teams or a broader technical domain. These roles follow a specialist career path without line management responsibilities.

The GitLab and Monzo frameworks agree on this distinction in scope, without establishing universal equivalence between grades. Staff Engineers address their team's most complex challenges, among other responsibilities, and have influence beyond the team. Principal Engineers focus more on architecture decisions and changes affecting several teams. When defining a role, specify the systems involved, the decisions entrusted to the person and the people they will need to work with.

This expertise remains grounded in delivery. It involves design, implementation, code review and support for engineers. The autonomy expected includes the ability to clarify an initially ill-defined problem and then lead its resolution with the teams. It does not mean working alone or deciding on the company's entire architecture.

Staff / Principal Engineer, Tech Lead and Engineering Manager: who does what?

• Staff / Principal Engineer: provides expertise to solve complex problems and contribute to technical decisions, within one team or across several teams depending on the role.
• Tech Lead: provides technical leadership for projects.
• Engineering Manager: takes responsibility for line management of engineers.

Reporting lines and decision-making authority must be explicit within your organisation. In particular, specify who resolves technical disagreements and how those decisions fit with the priorities of engineering and product leadership.

A technical problem can extend beyond the responsibilities of a single team. An architecture change, a performance issue or a modification to connected systems then requires an understanding of how decisions will affect other projects. The Staff / Principal Engineer brings the ability to handle this complexity and align technical decisions more closely with the organisation's objectives.

The role also matters for teams' ability to carry on with the work. The frameworks associate it with mentoring and engineers' autonomy. Employers should therefore look for expertise that the person can explain and share. An expert whose input becomes essential to every decision risks undermining this goal of autonomy.

Hypothetical example: several teams need to modify connected systems, but their proposals rely on different assumptions. Task the person you are looking to hire with clarifying dependencies, comparing solutions and preparing a phased rollout.

An unclear role definition can lead to hiring someone highly skilled in a technology without giving them access to the decisions that justify their position. It can also create conflict with existing technical leaders.

Finally, distinguish the quality of a proposal from its feasibility in practice. Performance, reliability and maintainability constraints need to be discussed with the teams that will develop the systems further. A technically convincing choice may still be unsuitable if its consequences for those teams have not been examined. Candidate assessment should therefore consider their reasoning, their contribution to implementation and how they reach agreement.

• Clarify complex technical problems and the constraints of the systems involved.
• Design solutions and compare their effects on performance, reliability and software quality.
• Lead architecture changes with the teams whose systems are affected.
• Connect technical proposals to departmental objectives and project priorities.
• Help implement solutions and support their phased rollout.
• Improve development practices, code reviews and the management of technical debt.
• Help engineers take on more technical responsibility and become more autonomous.
• Explain decisions and coordinate discussions between engineering, product and other relevant disciplines.

Relevant capabilities develop through work on complex software projects, from formulating a proposal to production deployment. Designing a solution, discussing it with other engineers and helping to implement it prepares someone to evolve an architecture with a team.

Initial education can contribute to these capabilities, but the frameworks examined establish neither a compulsory qualification nor a minimum length of experience for this role. The responsibilities held, the difficulty of the problems tackled and the interactions between systems characterise a person's background beyond years of experience. The indicators in the salary table are therefore not education or training prerequisites.

Production experience teaches engineers to analyse the consequences of technical decisions and make trade-offs between performance, reliability and software quality.

Preparation for the role also includes cooperation and support for engineers. Helping colleagues solve a problem or take on more responsibility develops the ability to share expertise. These capabilities matter in a role whose influence extends beyond individual work on code.

The assessment presented here combines the general foundations of the GetPro method with advice to adapt to the Staff / Principal Engineer role.

The foundations of the GetPro method

GetPro structures assessment around a prioritised set of criteria. It distinguishes what can be verified in a candidate's background from what requires a discussion or test. Each criterion is linked to an assessment method, and the criteria guide interviews towards areas that still need further exploration.

During interviews, key criteria are explored through open questions and concrete examples. Reference checks help cross-check the information gathered and shed light on areas that need attention. Questions place skills in the context of collaboration and ask for examples of how they have been used in practice.

Advice on adapting the assessment to a Staff / Principal Engineer

1. Define the criteria before interviews

Describe the problems the person will need to address, the systems involved and the teams they will work with. Distinguish the decisions they will be able to make from those requiring approval.

Build a set of criteria around design, implementation, software quality and cooperation. Specify your expectations for each criterion. Avoid inferring a candidate's level from their previous title alone.

Involve someone in the assessment who can discuss architecture decisions and their implementation. If this expertise is lacking internally, seek a technical assessor with expertise in the systems involved.

2. Examine past work

Ask the candidate to present a complex project to which they contributed directly. Ask them to clarify the initial problem, the constraints and the decisions for which they were responsible.

Explore choices of programming language, data structures and trade-offs between performance and reliability where relevant. Also discuss security considerations specific to the project.

Distinguish their personal contribution from the team's work. A clear explanation of the options considered and the consequences observed is a positive sign. Probe answers that focus on the team's overall success without specifying what the candidate personally delivered.

3. Discuss a design scenario

Choose a hypothetical problem close to the responsibilities of the role. Provide enough context for the candidate to question the constraints, without prescribing a solution at the outset.

Hypothetical example: ask how to evolve a system connected to other applications when performance problems arise. Ask the candidate to explain what information they would gather before changing its architecture.

Invite the candidate to represent interactions between systems using a shared drawing tool or surface. Examine how the candidate compares options and then plans implementation and a phased rollout.

Value questions that help inform the decision. A solution proposed immediately, without examining the constraints, warrants further discussion of the reasoning behind it.

4. Assess cooperation and knowledge sharing

Ask for an example of a technical disagreement involving several people. Ask the candidate to explain the arguments exchanged, how the decision was reached and their personal role.

Also explore a situation in which they supported an engineer. Look for what the candidate passed on and how their colleague was able to become more autonomous.

Distinguish technical influence from line management. The ability to explain how agreement was reached is a positive sign. Probe accounts in which the person decides alone without describing the other teams' constraints.

5. Cross-check the evidence and make a decision

With the candidate's agreement, use references to clarify their contribution to the projects discussed, their cooperation and their support for engineers. Ask questions linked to the criteria defined at the outset.

Then bring together the assessors' observations. Separate demonstrated capabilities from areas that still need further exploration. Base the decision on the responsibilities of the role, making any support needs explicit.