We promote seniors for deep output: hard bugs, hard designs, hard deploys. That is fair. It is incomplete.
A senior who cannot teach becomes a single point of failure with equity. A senior who can teach becomes a growth engine.
Seniority is leverage, or it is theater
Real senior leverage looks like:
- a mid-level engineer shipping a pattern the senior introduced last month
- a PR review that upgrades the author’s mental model
- a short doc that prevents five Slack threads
- a calmer incident because more people understand the failure domain
If none of that happens, you do not have leverage. You have a talented individual contributor with a senior title.
Teaching is part of the job description
I expect seniors on my teams to:
- leave readable decisions, not tribal knowledge
- review for growth, not only correctness
- invite others into production ownership safely
- say “watch how I cut this” before they vanish into a hero branch
That expectation has to be rewarded. If you only praise firefighting, you will get firefighters. If you praise teaching, you will get teachers.
The fear that teaching creates competition
Some strong engineers quietly fear that teaching makes them replaceable. In healthy companies, replaceability is the point. It is how teams survive. It is how people get promoted into broader scope. It is how the company opens a second product line without cloning one brain.
Replaceability through teaching is not disrespect. It is professionalism.
How I coach seniors into teaching
Not everyone is a natural mentor. That is fine. Start small:
- narrate tradeoffs out loud in planning
- write one ADR after a heated decision
- take a mid-level through the first production deploy of a subsystem
- turn a repeated review comment into a short guide
Teaching is a skill. Skills improve with reps.
Leadership takeaway
If you want the company to grow, stop treating teaching as volunteer charity work. Make it a senior expectation, a promotion signal, and a delivery strategy.
The best seniors do not only raise the ceiling of what they can build. They raise the floor of what the team can build without them.