Senior Engineer Ownership Scope at 10–20 Engineers: Clarity for CTOs
You must define formal ownership boundaries before hitting 20 engineers, or roles get messy as you scale
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Joseph KaplanRelated reading
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TL;DR
- Senior engineers in 10–20 person teams own full features or subsystems, not just code
- Their scope grows from tickets to cross-team coordination, technical decisions, and mentoring 1–3 juniors
- At this stage, you need at least one dedicated engineering manager for people ops while seniors focus on execution and architecture
- Keeping seniors as pure ICs past 15 engineers causes bottlenecks and slows decision-making
- You must define formal ownership boundaries before hitting 20 engineers, or roles get messy as you scale
Defining Senior Engineer Ownership Scope at 10–20 Engineers
Senior engineers here own whole features or systems end-to-end, making technical decisions that impact 3–5 other engineers. Their work goes beyond code - they handle architecture, risk, and cross-team work.
Key Responsibilities and Accountabilities
Core Ownership Areas
- Own 1–2 major product features or infrastructure systems with full delivery accountability
- Make architectural decisions in their domain, no CTO/VP signoff needed
- Debug and resolve incidents in owned systems
- Review code for 3–5 engineers, enforce standards, teach design patterns
- Break down quarterly roadmap into actionable tasks
Decision Authority
| Decision Type | Senior Engineer Authority | Requires Escalation |
|---|---|---|
| Technology choice in owned system | Full authority | No |
| Breaking API changes affecting other teams | Propose and coordinate | CTO or tech lead approval |
| Infra cost increases < $500/month | Yes | No |
| Hiring decisions for team | Input and technical screens | Final decision with eng manager |
| Timeline commitments for owned features | Yes, with manager visibility | No |
Delivery Expectations
- Ship high-quality code 60–70% of the time
- Spend 30–40% on design reviews, mentoring, incident response
- Unblock 2–3 engineers per week via technical guidance
Scope Evolution at Growing Team Sizes
| Team Size | Senior Engineer Scope | Reporting/Collaboration | Key Responsibilities |
|---|---|---|---|
| 10 | Owns 1 full-stack feature | Reports to CTO/founding engineer | Makes most tech decisions independently |
| 15 | Owns backend or frontend of 2–3 features | Works with 1–2 senior peers | Mentors mid-level engineers |
| 20 | Owns complete service or product area | Coordinates with 2–3 seniors | Leads small teams, aligns with standards |
- Between 15–20 engineers, companies introduce formal levels and scope.
- Seniors shift from generalists to domain experts with clear system boundaries.
Operational Risk, Architectural Risk, and Tradeoffs
Risk Ownership Matrix
| Risk Category | Senior Engineer Manages | Escalates to CTO/Leadership |
|---|---|---|
| Service downtime in owned system | Yes, owns incident response | Multi-service outages |
| Technical debt in owned features | Yes, proposes remediation plan | Debt blocking new feature work |
| Security vulnerabilities in code | Yes, patches within SLA | Customer data exposure |
| Scalability bottlenecks | Yes, implements fixes | Needs infra budget increase |
| Breaking changes during deploys | Yes, manages rollout strategy | Changes affecting revenue systems |
Common Tradeoffs Navigated
- Speed vs. quality: Ship MVP fast or wait for polish?
- Build vs. buy: Write custom or use third-party?
- Generalization vs. specificity: Design reusable or fix immediate need?
- Team autonomy vs. standardization: Use different tools or align with org?
Rule → Example
Rule: Document all significant tradeoff decisions in a design proposal. Example: "We chose Redis over Memcached for session storage - see design doc ADR-24."
Architectural Risk Boundaries
- No new languages without CTO signoff
- Don’t introduce distributed systems patterns the team can’t operate
- Avoid DB tech changes affecting shared infra
- Don’t alter auth/authorization across services solo
Role Structures and Execution Models In Scaling Engineering Teams
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Ownership Distribution: Tech Lead, Project Management, and Mentorship
| Role | Primary Responsibility | Does Not Own |
|---|---|---|
| Tech Lead | System design, architecture, technical direction | Career development, hiring decisions |
| Engineering Manager | Team output, growth, hiring | Day-to-day technical decisions |
| Senior Engineer | Component ownership, mentorship, code review | Cross-team prioritization, resource allocation |
Tech Lead Execution Model
- Owns technical strategy for 1–2 major systems (backend, CI/CD, microservices)
- Runs design reviews before builds start
- Makes final calls in tech debates
- Doesn’t write tickets for others
Senior Engineer Ownership Scope
- Owns entire subsystems, breaks down work for self and 1–2 juniors
- Runs code reviews for their area
- Mentors through pairing, not formal check-ins
Rule → Example
Rule: Senior engineers can approve technical changes within their subsystem without manager approval. Example: "Upgrading Node.js in the payments service - approved by senior engineer."
Processes: Code Reviews, Collaboration Tools, and Documentation
| Team Size | Review Model | Approval Requirement |
|---|---|---|
| 5–10 | Any senior reviews | 1 approval |
| 10–20 | Round-robin rotation | 2 approvals for core systems |
| 20+ | Domain-specific reviewers | Tiered, based on risk |
Essential Collaboration Infrastructure
- Documentation platform (Notion, Confluence, or wiki) with design doc templates
- Async decision tracking (GitHub issues, Linear)
- Runbook repository for DevOps and incident response
- ADRs (Architecture Decision Records) in version control
Review Process Requirements
- All backend design changes require a written design doc
- CI/CD changes must be tested in staging first
- Microservices interfaces need API contract review before building
- Production deploys follow a release checklist with rollback plan
Senior engineers enforce these standards. They block changes that skip steps - even under speed pressure.
Common Pitfalls and Practical Examples at 10–20 Engineers
| Pitfall | Symptom | Fix |
|---|---|---|
| Centralized backlog grooming | Manager writes all tickets | Seniors decompose epics themselves |
| Tech Lead bottleneck | All decisions wait for one | Define decision domains, clear owners |
| No design review | Costly rewrites after months | Require written designs >3 days work |
| Over-hiring into dysfunction | More engineers, less output | Output metrics before headcount grows |
Real Scenarios
- Startups growing from 8 to 15 engineers: Managers become project bottlenecks by writing all tickets and planning sprints. Seniors need to own feature areas, write technical plans, and break down work.
- Facebook: Senior engineers own feature areas, handle technical planning, and coordinate cross-team. Managers give context but don’t make execution plans.
- Manufacturing companies shifting to software: Centralizing tech decisions with one architect causes delays. Distribute architecture authority by system.
Common Anti-Pattern: The TLM Role
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| Role Problem | Why It Fails at 10–20 Engineers | Solution |
|---|---|---|
| Tech Lead Manager (TLM) | One person can’t own growth, hiring, and technical direction | Split into two roles or accept mediocre performance |
Frequently Asked Questions
What responsibilities does a senior engineer have when leading a team of 10-20 engineers?
Core Leadership Responsibilities
- Define technical direction, approve architecture for subsystems
- Review code and design proposals
- Own on-call rotation and production reliability
- Break down big projects into assignable work
- Manage technical debt and core IP improvements
Team Scaling Duties
- Mentor mid-levels on design and ownership
- Distribute code review via round-robin
- Set style guides for code simplicity
- Run design reviews for large projects
Manager Collaboration
- Partner with managers on growth plans
- Identify engineers for customer vs. internal work
- Recommend team changes if mentorship bottlenecks appear
Rule → Example
Rule: Use distributed ownership structures to create space for multiple strong leaders. Example: "Senior engineers each own a product area and lead their own design reviews."
How does senior engineer role and scope differ between companies like Amazon and Google?
| Aspect | Amazon Approach | Google Approach |
|---|---|---|
| Team size | Small teams (6-8), tight ownership | Larger teams (10-15), broader scope |
| Project structure | Seniors own full verticals | Matrix teams, shared components |
| Production | Full stack, including ops | SRE teams handle production |
| Code review | Seniors have final approval | Multiple tech leads review |
Decision-Making Authority
- Amazon: Seniors own entire service boundaries, make infra choices
- Google: Seniors work within established infra, focus on optimization
Career Progression
- Amazon: Promotion tied to end-to-end ownership, 2–3 direct mentees
- Google: Promotion tied to technical complexity and cross-team impact, 5–10 mentees influenced via design reviews
What experience level is typically required for an engineer to reach L5 at a major tech company?
Years of Experience by Track
| Company | L5 Title | Typical Years | Experience Requirements |
|---|---|---|---|
| Senior Software Engineer | 6–8 years | Led 2+ major projects affecting multiple teams | |
| Meta | E5 | 5–7 years | Designed systems serving 100M+ users |
| Amazon | SDE III | 5–7 years | Owned service with 99.99% uptime requirements |
| Microsoft | Senior Engineer | 6–9 years | Shipped features used by 10M+ customers |
Technical Scope Markers
- Design distributed systems handling 10,000+ requests/sec
- Lead technical decisions that impact 3+ teams, no manager sign-off needed
- Mentor 2–3 mid-level engineers through project delivery
- Debug production incidents in services outside your own codebase
Promotion Velocity Factors
| Track | Timeline | Key Criteria |
|---|---|---|
| Fast track | 4–5 years | Core infra, high visibility projects |
| Standard | 6–8 years | Customer-facing features, steady complexity |
What is the expected salary range for a senior staff engineer at top aerospace and defense companies?
Base Compensation Ranges
| Company Type | Senior Engineer | Staff Engineer | Geographic Premium |
|---|---|---|---|
| Defense primes (Lockheed, Raytheon) | $125k–$165k | $155k–$195k | 15–20% for CA/DC |
| Aerospace (Boeing, SpaceX) | $135k–$175k | $165k–$205k | 25–30% for CA/WA |
| Defense tech (Palantir, Anduril) | $165k–$210k | $200k–$260k | 30–40% for big metros |
Total Compensation Components
- Base salary: 75–85% of total comp
- Equity grants: smaller, vest over 3–4 years
Clearance Impact
| Clearance Type | Base Salary Premium | Total Comp Example (Staff) |
|---|---|---|
| TS/SCI | +$15k–$25k | $180k–$220k |
| Polygraph | +$10k–$15k | |
| No clearance | - | $140k–$175k |
- Security clearances set salary floors; cleared engineers are hard to replace
How does the engineer leveling system (e.g., levels 1–4) impact the scope of ownership for senior engineers?
Ownership Scope by Level
| Level | Ownership Boundary | Team Interaction | Decision Authority |
|---|---|---|---|
| L3 (Mid) | Single feature/component | Works within team | Proposes technical approaches |
| L4 (Senior) | Full service/subsystem | Influences 1–2 teams | Approves designs for owned area |
| L5 (Staff) | Multiple related services | Coordinates 3–5 teams | Sets technical direction |
| L6 (Principal) | Platform/product area | Aligns 5–10 teams | Defines architecture standards |
Delegation Patterns
- L3: Gets detailed tasks from seniors
- L4: Receives goals, creates execution plans
- L5: Gets business objectives, proposes solutions
Review Requirements
| Level Reviewed | Reviewer Level | When Required |
|---|---|---|
| L3 | L4+ | Before implementation |
| L4 | L5+ | For large, multi-team projects |
| L5 | L6+ | When setting new architectural patterns |
| L6 | Director | For platform-level changes |
Role Shift Rule → Example
Rule: Senior engineers balance technical execution with leadership; staff engineers focus on vision and strategy.
Example: "As a staff engineer, I set product direction and mentor teams, not just write code."
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