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name: senior-software-engineer description: | Guides senior software engineering across languages and stacks—system and service design, RFCs, code review, refactoring, reliability patterns, testing strategy, performance analysis, technical decomposition, and engineering leadership on delivery teams. Use when designing services or modules, writing technical specs, reviewing PRs for architecture and correctness, improving legacy code, choosing trade-offs (coupling, consistency, latency), estimating complex work, or mentoring engineers—not for stack-specific full-stack UI delivery (senior-fullstack-developer), deployment rollout strategy (deployment-strategist), infrastructure/IaC (infrastructure-engineer), dedicated perf profiling and load testing (performance-engineer), org-wide security programs (cybersecurity), or cross-system ADRs and architecture review (senior-system-architecture).

Senior Software Engineer

When to Use

• Design services, modules, APIs, or technical approaches across general software stacks
• Write RFCs, technical specs, decomposition plans, or engineering trade-off analysis
• Review PRs for correctness, maintainability, reliability, operability, and test coverage
• Refactor legacy code safely while preserving behavior
• Mentor engineers on implementation quality, estimates, and delivery risks

When NOT to Use

• Build stack-specific full-stack product features end to end → senior-fullstack-developer, fullstack-software-engineer
• Focus only on React/UI architecture and accessibility → senior-frontend-software-engineer
• Choose rollout plans, canaries, or cutover strategy → deployment-strategist
• Provision infrastructure, Kubernetes, or IaC → infrastructure-engineer
• Make enterprise-wide architecture decisions or ADR review gates → senior-system-architecture

Related skills

Need	Skill
React/Next + vertical feature delivery	fullstack-software-engineer, senior-fullstack-developer
Senior front-end architecture and a11y	senior-frontend-software-engineer
Rollout plans and release strategy	deployment-strategist
CI/CD implementation	devops
Cloud/K8s/Terraform	infrastructure-engineer
Requirements and BRDs	business-analyst
AI/LLM product features	ai-engineer
Cross-service ADRs, NFRs, architecture review	senior-system-architecture
Profiling, load tests, latency SLOs	performance-engineer

Core Workflows

1. Technical design (RFC)

1. State problem, constraints, and non-goals
2. List options with trade-offs (at least two alternatives)
3. Recommend one; define interfaces and data contracts
4. Identify risks: scale, failure modes, migration, operability
5. Define success metrics and rollout approach (link deployment-strategist if needed)

Deliverable: short RFC or design doc with diagram (C4 or sequence for critical paths).

See references/system_design.md for templates, boundaries, and consistency patterns.

2. Implementation planning

Break work into:

Slice	Outcome
Foundation	Types, interfaces, skeleton with tests
Core behavior	Happy path end-to-end
Edge cases	Errors, idempotency, authz
Operability	Logs, metrics, runbooks
Cleanup	Remove flags, deprecate old path

Estimate each slice; call out unknowns and spikes.

See references/rfc_technical_leadership.md for estimation and decomposition.

3. Code review (senior bar)

Review order: correctness → design → operability → style.

Check	Question
Correctness	Edge cases, races, error handling
API design	Clear contracts, backward compatibility
Security	Authz, injection, secrets
Tests	Meaningful cases, not snapshot noise
Operability	Logs, metrics, configurable limits
Maintainability	Coupling, naming, duplication

Leave actionable comments; distinguish blocker vs nit.

See references/code_review.md for rubric and comment patterns.

4. Refactoring and quality

When to refactor: before adding feature in tangled module, or when change touches same area third time.

Approach:

1. Add characterization tests around behavior
2. Small commits: extract → rename → move
3. Preserve external behavior; use feature flags for risky swaps
4. Delete dead code in same PR when safe

See references/refactoring_quality.md for smells and safe sequences.

5. Reliability and performance

Reliability defaults:

• Timeouts on all outbound calls
• Retries with jitter only for idempotent ops
• Circuit breakers at integration boundaries
• Graceful degradation with clear user messaging

Performance:

1. Measure (profiler, traces, query plans)—no premature optimization
2. Fix N+1, unnecessary allocation, hot loops
3. Cache with explicit TTL and invalidation story

See references/reliability_patterns.md for distributed systems primitives.

6. Technical leadership

• Unblock others: pair on hard bugs, clarify design decisions in writing
• Raise risks early; propose phased delivery
• Document decisions in ADR when reversal is costly
• Align with product on scope vs quality trade-offs

See references/rfc_technical_leadership.md for ADRs and mentoring prompts.

When to load references

• Service design and RFCs → references/system_design.md
• PR review → references/code_review.md
• Refactoring → references/refactoring_quality.md
• Reliability and performance → references/reliability_patterns.md
• Estimation, ADRs, mentoring → references/rfc_technical_leadership.md