What makes a principal engineer different from a senior?
I recently watched an insightful video featuring Steve Hume, who spent 17 years as a Principal Engineer at Amazon. He shared a great deal about the company’s engineering culture, but what I found most interesting was his breakdown of the Principal Engineer role. It is not just the next step on the ladder; it is a leap into a different, and often more challenging, type of work.
The role is not about being the best coder; it is about navigating ambiguity and wielding influence, often with significant trade-offs.
The leap from senior to principal
At many companies, the path from Senior to a role like Staff or Principal is a linear progression. At Amazon, the path is deliberately different. They largely omit the “Staff Engineer” level, creating a huge step between Senior (L6) and Principal (L7). Hume notes the promotion is incredibly difficult, with thousands of Senior Engineers competing for a few hundred Principal roles.
A Senior Engineer at Amazon is a force within their team. They are expected to deliver complex projects and, crucially, own their services end-to-end. As Hume puts it, “At Amazon, you don’t just build it—you’ll be paged at 3 AM when it breaks in production.” They lead through influence and documentation within their domain, but they cannot command other teams to do work. Their autonomy is bounded by their team’s scope.
The Principal role is a fundamental shift in three key areas.
1. From solving problems to defining the problem space
This is the most critical differentiator. A Senior Engineer solves a given problem. A Principal Engineer is given a vague business objective and must first define the problem itself, and then expand the entire menu of possible solutions.
When a VP says, “Improve availability for our NFL streams,” the Principal’s job is not to start optimising code. It is to ask:
- Should we re-architect the service?
- Should we buy a third-party solution?
- Should we reallocate engineers from a lower-priority team to this problem?
- Is this even the right problem to solve to achieve the business goal?
They might even decide to kill a project if it is not the highest-impact work. This is about strategic leverage, not just technical execution.
2. Autonomy with high-stakes accountability
The role is not about “freedom from micromanagement.” It is about being thrust into ambiguity with high-stakes accountability. As Hume says, “A VP tells you the direction, not the steps.”
A Principal is expected to take that vague directive and deliver a transformative solution without hand-holding. The other side is that if they fail, the consequence is not a performance improvement plan; it is a loss of trust from senior leadership. The feedback would be, “This is not what I expected from a Principal.” That is a career-limiting outcome.
3. Influence over authority: The paradox of belonging
Hume describes the Principal experience with a compelling phrase: “You belong everywhere and nowhere.”
This is not just about floating between teams; it is a significant psychological and political challenge. Principals operate in the gaps, which means they are constantly having to rebuild context in new domains. They often face friction from teams who may resent an “outsider” parachuting in to give advice.
Because they have no direct authority, they must lead entirely through influence. They work with teams by challenging assumptions, connecting people to avoid duplicated work, and using data and well-structured arguments (like the ‘six-pagers’) to build consensus. They act as guides and guardrails, not commanders. This status also leads to extreme bandwidth challenges, forcing them to prioritise ruthlessly, often at the expense of hands-on coding.
How this compares to our own expert roles
This analysis makes the comparison to my own company’s structure much sharper. We have technical experts who are the highest authority within a specific domain. This model prioritises depth. Our experts have deep, long-term context and ownership, which is invaluable for core business areas.
Amazon’s model is structurally different and deliberately so. By avoiding domain-aligned Principals, they force them to develop breadth. Their value comes from identifying and solving systemic, cross-organisational problems that no single team can see or solve.
The trade-off is clear. Our model builds world-class specialists but may struggle to address issues that span multiple domains. Amazon’s model is designed to fix those systemic issues but means its Principals may lack the deep, focused expertise that our roles cultivate. Neither is inherently better, but they are optimised for different goals.
The video was an interesting look into a role defined by its trade-offs: influence over hands-on coding, breadth over depth, and autonomy at the cost of extreme accountability.
You can watch the full video here: What is a Principal Engineer at Amazon? With Steve Huynh.
