feat(Infrastructure): Challenge candidates with Kubernetes problems

.github/workflows/k8s-challenger-lint.yml

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+name: k8s-challenger-lint
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "kubernetes/**"
+      - ".github/workflows/k8s-challenger-lint.yml"
+  pull_request:
+    branches: [main]
+    paths:
+      - "kubernetes/**"
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    name: Lint k8s_challenger Python code
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.14"
+          cache: "pip"
+          cache-dependency-path: "kubernetes/pyproject.toml"
+
+      - name: Install dependencies
+        working-directory: kubernetes
+        run: pip install -e ".[dev]"
+
+      - name: Lint with Ruff
+        working-directory: kubernetes
+        run: ruff check cli/
+
+      - name: Type check with ty
+        working-directory: kubernetes
+        run: ty check cli/

kubernetes/.gitignore

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+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+*.egg-info/
+dist/
+build/
+*.egg
+
+# Virtual environments
+venv/
+env/
+ENV/
+.venv
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+.DS_Store
+
+# Testing and linting
+.pytest_cache/
+.coverage
+.mypy_cache/
+.ruff_cache/
+htmlcov/
+
+# Docker volumes and runtime
+kubeconfig/
+*.log
+
+# Environment files
+.env
+.env.local
+
+# Temporary files
+*.tmp
+*.bak

kubernetes/CONTRIBUTING.md

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+# Contributing to Flagsmith Interview Challenges
+
+This guide explains how to create, validate, and maintain interview challenges for the Flagsmith challenge system.
+
+## Requirements
+
+Every challenge **MUST** consist of:
+
+1. **Challenge Definition** (`{name}.yaml`)
+   - Name, description, estimates, helm values, kubectl patches
+
+2. **Reviewer Manual** (`{name}.md`)
+   - Step-by-step solution guide for the interviewer
+   - Educational learning points
+   - Debugging techniques and prevention strategies
+
+3. **Required YAML Fields**
+   ```yaml
+   name: "Challenge Title"
+   description: "Candidate must [action] to fix [issue] causing [symptom]"
+   estimates:
+     Lv1: <integer>    # Bronze: 0-2 years K8s experience
+     Lv2: <integer>    # Silver: 2-4 years K8s experience
+     Lv3: <integer>    # Gold: 4+ years K8s experience
+   helm_values: {}     # Helm chart configuration
+   kubectl_patches: [] # Optional kubectl JSON patches
+   ```
+
+All fields are mandatory. The system will fail immediately if any required field is missing or if the corresponding `.md` manual doesn't exist.
+
+## Creating a Challenge
+
+### Step 1: Define the Challenge
+
+Create a new YAML file in `challenges/` with your challenge definition.
+
+**Requirements:**
+- Filename must be kebab-case: `my-challenge.yaml`
+- Must include all required fields
+- `name` should be descriptive and clear
+- `description` should follow the pattern: "Candidate must [action] to fix [issue] causing [symptom]"
+- Time estimates should be realistic integers (not `∞` unless unsuitable for that level)
+
+**Example:**
+```yaml
+name: "Database Connection Timeout"
+description: "Candidate must identify and fix connection pool exhaustion causing timeout errors."
+estimates:
+  Lv1: 30
+  Lv2: 15
+  Lv3: 8
+
+helm_values:
+  api:
+    replicaCount: 1
+    resources:
+      limits:
+        cpu: "100m"
+        memory: "256Mi"
+
+kubectl_patches:
+  - resource: "deployment"
+    name: "flagsmith-api"
+    namespace: "flagsmith"
+    patch_type: "json"
+    patch:
+      - op: "add"
+        path: "/spec/template/spec/containers/0/env/-"
+        value:
+          name: "DB_POOL_SIZE"
+          value: "1"
+```
+
+### Step 2: Write the Reviewer Manual
+
+Create a corresponding `.md` file with the same name: `my-challenge.md`
+
+**Required sections:**
+
+1. **Problem Description** - What's broken and why
+2. **Step-by-Step Solution** - Each debugging step with commands and expected output
+3. **Key Learning Points** - Educational objectives (5-7 bullet points)
+4. **Prevention** - How to avoid this in production
+5. **Additional Debugging Commands** - Extra tools and techniques (optional but recommended)
+
+**Structure Example:**
+```markdown
+# Challenge: Database Connection Timeout - Solution
+
+## Problem Description
+[Explain what's broken and the root cause]
+
+## Step-by-Step Solution
+
+### Step 1: Identify the Problem
+[Commands and expected symptoms]
+
+### Step 2: Investigate the Configuration
+[Debugging commands with output]
+
+[Continue with numbered steps...]
+
+## Key Learning Points
+
+1. [Educational point 1]
+2. [Educational point 2]
+[etc...]
+
+## Prevention
+
+- [Prevention strategy 1]
+- [Prevention strategy 2]
+
+## Additional Debugging Commands
+
+[Optional reference commands]
+```
+
+### Step 3: Estimate Time Accurately
+
+Time estimates guide interviewer expectations and candidate assessment.
+
+**Guidelines:**
+- **Lv1 (Bronze)**: 0-2 years K8s experience, may need to Google commands
+- **Lv2 (Silver)**: 2-4 years, solid troubleshooting, familiar with tools
+- **Lv3 (Gold)**: 4+ years, senior/staff level, can diagnose quickly
+
+**Mark as Unsuitable:**
+Use `"∞"` (infinity symbol) for Lv1 if the challenge is unsuitable for beginners:
+```yaml
+estimates:
+  Lv1: "∞"    # Senior-level challenge, unsuitable for beginners
+  Lv2: 20
+  Lv3: 9
+```
+
+**Estimation Guidelines:**
+- Simple challenge (e.g., single configuration error): 15-25 minutes for Lv1
+- Moderate challenge (multi-step debugging): 30-45 minutes for Lv1
+- Complex challenge (multiple concurrent issues): 45-60 minutes for Lv1, or mark as `"∞"`
+- Senior-level candidates (Lv3): Typically complete challenges in 5-15 minutes
+
+## Validation Checklist
+
+Before submitting a challenge:
+
+- [ ] Both files exist: `challenges/my-challenge.yaml` and `challenges/my-challenge.md`
+- [ ] YAML contains all required fields: `name`, `description`, `estimates`, `helm_values`, `kubectl_patches`
+- [ ] Time estimates are positive integers or `"∞"` where appropriate
+- [ ] Helm values deploy successfully
+- [ ] kubectl patches use valid JSON syntax
+- [ ] Challenge deployment is actually broken (health check fails)
+- [ ] Solution manual is technically accurate and matches the challenge
+- [ ] Time estimates are realistic (verified through manual walkthrough)
+
+## Testing Your Challenge
+
+Run the system and test your challenge:
+
+```bash
+make run
+```
+
+Then:
+1. Select your challenge from the menu
+2. Verify it deploys successfully
+3. Confirm the challenge is actually broken (health check fails)
+4. Work through the solution steps in your manual
+5. Verify time estimates are realistic for each skill level
+6. Confirm the health endpoint returns 200 after your fixes
+
+## Code Quality
+
+All Python code must pass linting and type checking:
+
+```bash
+ruff check cli/
+ty check cli/
+```
+
+Challenge files are discovered automatically. No code changes are needed when adding new challenges.
+
+## Challenge Consistency
+
+### Naming Conventions
+- Use kebab-case for filenames: `network-issue.yaml`, not `NetworkIssue.yaml`
+- Use Title Case for `name` field in YAML
+- Keep names concise but descriptive
+
+### Description Format
+Follow this pattern:
+> "Candidate must **[action]** to fix **[issue]** causing **[symptom]**."
+
+**Good examples:**
+- "Candidate must identify and fix a typo in the database service name causing connection failures."
+- "Candidate must remove a CPU-intensive sidecar container causing API performance issues."
+- "Candidate must adjust memory limits that are set too low causing OOMKilled pods."
+
+**Bad examples:**
+- "There's a broken pod" (vague)
+- "Fix this" (unclear)
+- "Challenge about networking" (not action-oriented)
+
+### Patch Format
+Use JSON patches with proper escaping for special characters:
+```yaml
+# Correct: Use ~1 for forward slash in JSON pointer
+path: "/spec/selector/app.kubernetes.io~1name"
+
+# Wrong: Don't use literal forward slash
+path: "/spec/selector/app.kubernetes.io/name"
+```
+
+## Educational Standards
+
+### What Makes a Good Challenge?
+
+**Characteristics of effective challenges:**
+- Tests real-world debugging skills and systematic troubleshooting
+- Clear root cause that candidates can identify through investigation
+- Teaches production-relevant concepts and best practices
+- Multiple valid approaches to reach the solution
+- Objective success criteria (health endpoint returns HTTP 200)
+
+**What to avoid:**
+- Ambiguous symptoms that could indicate multiple unrelated issues
+- Contrived scenarios that wouldn't occur in real environments
+- Challenges requiring deep Flagsmith application knowledge (focus on Kubernetes)
+- Overly trivial fixes (unless teaching a specific lesson)
+- Subjective or unclear completion criteria
+
+### Learning Progression
+
+Design challenges across a spectrum of difficulty:
+
+1. **Beginner-friendly (Lv1)**: Single, well-defined issue with clear symptoms
+2. **Intermediate (Lv2)**: Multiple related issues requiring systematic debugging
+3. **Advanced (Lv3)**: Complex scenarios with concurrent problems, demanding deep expertise
+
+Each difficulty level should introduce new concepts or techniques, not just expect faster execution.
+
+## Maintenance
+
+### When to Update Challenges
+
+Update challenges when:
+- Time estimates prove inaccurate based on candidate performance
+- Debugging techniques or tools change
+- New Kubernetes best practices emerge
+- Technical inaccuracies are discovered in the solution
+
+### When to Mark as Unsuitable
+
+Use `"∞"` for specific levels when:
+- New tooling makes the challenge trivial for that skill level
+- The scenario no longer reflects realistic production issues
+- The educational value no longer justifies the time investment
+
+## Questions?
+
+Review existing challenges in the `challenges/` directory for working examples. The system enforces these requirements to maintain consistency and educational quality across all challenges.

kubernetes/Makefile

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+.PHONY: run help clean
+
+# Default target
+help:
+	@echo "Available commands:"
+	@echo "  make run    - Start the Flagsmith interview challenge system"
+	@echo "  make clean  - Clean up Docker resources"
+	@echo "  make help   - Show this help message"
+
+# Clean up project resources
+clean:
+	@echo "🧹 Cleaning up k8s_challenger resources..."
+	-docker-compose down --volumes --remove-orphans
+	-docker ps -a --filter "name=k8s_challenger" --format "{{.ID}}" | xargs -r docker rm -f
+	-docker volume ls --filter "name=k8s_challenger" --format "{{.Name}}" | xargs -r docker volume rm
+	@echo "✅ Cleanup complete"
+
+# Start the interview system with cleanup before and after
+run: clean
+	@echo "🚀 Starting Flagsmith Interview Challenge System..."
+	# Build images
+	docker-compose build cli candidate-env
+	# Start k3s in background
+	docker-compose up -d k3s
+	# Run CLI interactively
+	docker-compose run --rm cli
+	# Cleanup when done
+	$(MAKE) clean
+	@echo "✅ Session complete"