Service DesignFunctional RequirementService(s) ResponsiblePriorityScaling Characteristics
User Authentication	Auth Service	Critical	Read-heavy, cacheable tokens
Profile Management	User Service	High	Read-heavy, occasional writes
Workout Recording	Activity Service, Sensor Processor	Critical	Write-heavy, high-volume
Offline Tracking	Offline Sync Manager	High	Burst processing, conflict resolution
Goal Setting	Goal Service	Medium	Balanced read/write
Progress Visualization	Progress Service, Analytics Service	Medium	Read-heavy, computation intensive
Social Connections	Social Graph Service	Low	Graph operations, relationship-focused
Content Sharing	Feed Service	Low	Read-heavy, fan-out writes
Personalized Recommendations	Recommendation Engine, ML Pipeline	Medium	Compute-intensive, batch processing
Notifications & Reminders	Notification Service, Reminder Service	Medium	High throughput, time-sensitive
Device Integration	Device Service	High	Protocol translation, data normalization
Specialized Fitness Programs	Health Condition Adapter	Medium	Personalization-focused, rule-based

Enhanced Service Details

Activity Service (Critical Path Component)

Primary Responsibility:
- Record, validate, and process user workout data
- Ensure data integrity and consistent storage
- Support real-time and batch workout tracking
Internal Components:
- Activity Validator: Schema validation and data enrichment
- Metrics Calculator: Derived statistics computation
- Route Processor: GPS data analysis and smoothing
- Activity Repository: Storage abstraction with caching
State Management:
- Workout sessions use distributed state with sticky sessions
- Optimistic concurrency control with version vectors
- CQRS pattern with separate read and write models
- Event sourcing for critical workout data
Scaling Characteristics:
- Horizontal scaling based on active workout sessions
- Partition by user ID for data locality
- Auto-scaling triggered at 70% CPU utilization
- Specialized instances for data-intensive users
Resilience Patterns:
- Bulkhead pattern to isolate failures
- Retry with exponential backoff for transient failures
- Circuit breaker for dependent service calls
- Graceful degradation to core functionality

Recommendation Engine (AI-driven Component)

Primary Responsibility:
- Generate personalized workout suggestions
- Identify relevant challenges and goals
- Provide adaptive training plans
Internal Components:
- Feature Extractor: Processes user history into ML features
- Model Serving: Hosts trained ML models with A/B testing
- Recommendation Composer: Combines ML outputs with business rules
- Feedback Collector: Captures user responses to recommendations
AI Algorithms:
- Collaborative filtering for similar user patterns
- Gradient boosted trees for workout progression
- Deep learning for motion pattern analysis
- Reinforcement learning for adaptive plan optimization
Data Pipeline:
- Batch feature generation pipeline (daily)
- Real-time feature serving with feature store
- Hybrid serving with pre-computed and real-time features
- Continuous model evaluation with shadow testing
Scaling Characteristics:
- Compute-intensive batch processing
- GPU acceleration for model training
- Caching of recommendations with TTL-based invalidation
- Read replicas for feature serving

API Design

RESTful API Hierarchy

DomainResourceEndpointsVersioning
User	/users	GET, POST, PATCH, DELETE	v2
Authentication	/auth	POST /login, POST /refresh, POST /logout	v1
Activities	/activities	GET, POST, PATCH, DELETE	v3
Goals	/goals	GET, POST, PATCH, DELETE	v2
Social	/social	GET /feed, GET /connections, POST /share	v1
Devices	/devices	GET, POST, DELETE, POST /sync	v2
Recommendations	/recommendations	GET /workouts, GET /plans	v1

Enhanced API Examples

`Record Activity with Advanced Metrics`

コピー
POST /v3/activities
Content-Type: application/json
Authorization: Bearer {token}

Request Body:
{
  "activity_type": "strength_training",
  "start_time": "2025-03-28T16:30:00Z",
  "end_time": "2025-03-28T17:15:00Z",
  "metrics": {
    "energy_expenditure": {
      "calories": 320,
      "confidence": 0.92
    },
    "heart_rate": {
      "avg": 142,
      "max": 165,
      "zones": [
        {"zone": "easy", "time_seconds": 360},
        {"zone": "moderate", "time_seconds": 1200},
        {"zone": "intense", "time_seconds": 540}
      ]
    },
    "exercises": [
      {
        "name": "bench_press",
        "sets": [
          {"weight_kg": 80, "reps": 10, "rest_seconds": 90},
          {"weight_kg": 85, "reps": 8, "rest_seconds": 120},
          {"weight_kg": 90, "reps": 6, "rest_seconds": 150}
        ],
        "muscle_activation": {
          "pectoralis_major": 0.85,
          "anterior_deltoid": 0.65,
          "triceps_brachii": 0.55
        },
        "form_quality": 0.88
      }
      // Additional exercises...
    ]
  },
  "device_id": "garmin-fenix7-a12b3c",
  "notes": "Felt strong today, increased weight on final set",
  "training_factors": {
    "sleep_quality": "good",
    "nutrition_status": "well_fueled",
    "stress_level": "low"
  },
  "location": {
    "venue_id": "gym-123456",
    "coordinates": {"lat": 37.7749, "lng": -122.4194}
  }
}

Response (200 OK):
{
  "activity_id": "act-28a7eb9c420d",
  "status": "recorded",
  "processing_status": {
    "metrics_calculated": true,
    "insights_generated": "pending",
    "goal_progress_updated": true
  },
  "achievements": [
    {
      "id": "bench-press-personal-best",
      "title": "New Personal Best: Bench Press",
      "description": "You lifted 90kg, beating your previous best of 85kg"
    }
  ],
  "goal_impacts": [
    {
      "goal_id": "goal-78ad23",
      "title": "Weekly Strength Training",
      "progress": {
        "before": 0.66,
        "after": 0.83,
        "units": "completion_percentage"
      }
    }
  ],
  "recommendations": {
    "recovery": {
      "recommended_recovery_time_hours": 48,
      "focus_areas": ["chest", "shoulders"]
    },
    "next_workout": {
      "suggested_exercise_focus": "lower_body",
      "earliest_recommended_date": "2025-03-30T16:00:00Z"
    }
  }
}

Error Responses:
- 400: Invalid activity data
  {
    "error": "validation_error",
    "message": "Invalid activity data",
    "details": [{"field": "metrics.exercises[0].sets[1].weight_kg", "issue": "value must be numeric"}]
  }
- 401: Unauthorized
- 409: Conflicting activity record
  {
    "error": "conflict",
    "message": "An activity already exists within this time range",
    "conflicting_activity_id": "act-7862de1"
  }
- 429: Rate limit exceeded
  {
    "error": "rate_limited",
    "message": "Too many activity creations",
    "retry_after": 5
  }

`Get Personalized Recommendations`

コピー
GET /v1/recommendations/workouts
Content-Type: application/json
Authorization: Bearer {token}

Query Parameters:
- goal_focus: "strength" | "endurance" | "flexibility" | "weight_loss" | "overall"
- time_available_minutes: Integer (default: 60)
- equipment_available: Comma-separated list (default: "none")
- location: "home" | "gym" | "outdoors" (default: "home")
- intensity_preference: "light" | "moderate" | "challenging" (default: "moderate")

Response (200 OK):
{
  "recommendations": [
    {
      "id": "rec-34ab72d1",
      "title": "Upper Body Strength Circuit",
      "description": "A balanced upper body workout with focus on compound movements",
      "duration_minutes": 45,
      "difficulty": "moderate",
      "equipment_needed": ["dumbbells", "resistance_bands"],
      "muscle_groups": ["chest", "back", "shoulders", "arms"],
      "energy_expenditure": {
        "estimated_calories": 320,
        "range": {"min": 280, "max": 380}
      },
      "exercises": [
        {
          "name": "dumbbell_bench_press",
          "sets": 3,
          "reps": "8-10",
          "weight_guidance": "80% of your 12RM",
          "demonstration_video_url": "/assets/videos/dumbbell_bench_press.mp4",
          "alternatives": ["push_ups", "chest_press_machine"]
        },
        // More exercises...
      ],
      "personalization_factors": [
        "Based on your strength progress in the last 14 days",
        "Adjusted for your recovery status (well recovered)",
        "Complementary to your Tuesday workout pattern"
      ],
      "user_ratings": {
        "average": 4.7,
        "count": 1243
      }
    },
    // Additional recommendations...
  ],
  "meta": {
    "recommendation_freshness": "generated_today",
    "algorithm_version": "v2.3",
    "filtering_applied": ["excluded_recently_completed", "adjusted_for_equipment"]
  }
}

Error Responses:
- 400: Invalid parameters
- 401: Unauthorized
- 404: No suitable recommendations found
  {
    "error": "no_recommendations",
    "message": "No suitable workouts found for the specified parameters",
    "suggestions": [
      "Try increasing available time",
      "Add more available equipment options"
    ]
  }

Submissions

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Submissions

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