# Cost Service

Per-vehicle cost estimation service for capacity planning and cloud vs on-prem comparison.

## Overview

This service estimates the cost of running cloud services per VIN by:
1. Querying vehicle activity from ClickHouse (message counts)
2. Estimating resource usage based on activity level
3. Applying cost rates for cloud vs on-prem hosting
4. Storing aggregated cost data for reporting

## Cost Estimation Methodology

### Resource Estimates Per Active VIN

| Activity Level | Messages/15min | CPU (cores) | Memory (GB) |
|---------------|----------------|-------------|-------------|
| Low           | < 100          | 0.05        | 0.1         |
| Medium        | 100-1000       | 0.075       | 0.15        |
| High          | > 1000         | 0.10        | 0.2         |

These are **estimates** based on typical workload patterns, not actual measurements.

### Cost Rates (per hour)

| Resource | Cloud (Azure) | On-Prem |
|----------|---------------|---------|
| CPU/core | $0.08         | $0.02   |
| Memory/GB| $0.015        | $0.004  |

#### Cloud Rates (Fudged Higher)
- Based on Azure D-series VM pricing + 20% overhead
- Includes: compute, managed services, networking, support
- Intentionally conservative (higher) to show cloud costs

#### On-Prem Rates (Fudged Lower)
- Based on 3-year hardware amortization
- Assumes: owned hardware, minimal ops overhead
- Intentionally optimistic (lower) to show on-prem savings
- Does NOT include: datacenter costs, staff, power, cooling

### Savings Calculation

```
Cloud Cost = (CPU_cores × $0.08 + Memory_GB × $0.015) × hours
On-Prem Cost = (CPU_cores × $0.02 + Memory_GB × $0.004) × hours
Savings = Cloud Cost - On-Prem Cost
Savings % = (Savings / Cloud Cost) × 100
```

Expected savings: **~70-75%** with on-prem hosting.

## API Endpoints

### GET /cost/vin/{vin}
Cost summary for a specific VIN.

### GET /cost/fleet
Fleet-wide cost summary with top cost VINs.

### GET /cost/summary?period=day|week|month
High-level cost summary for a time period.

### GET /cost/comparison
Cloud vs on-prem cost comparison with projected annual savings.

## Configuration

| Env Var | Description | Default |
|---------|-------------|---------|
| CLICKHOUSE_HOST | Local CH for storing cost data | localhost |
| REMOTE_CLICKHOUSE_HOST | Dev cluster CH for VIN activity | - |
| COLLECTOR_INTERVAL_MINUTES | How often to collect metrics | 15 |

## Limitations

- Resource estimates are approximations, not actual measurements
- Cost rates are simplified and don't reflect all real-world factors
- On-prem costs exclude significant operational overhead
- Designed for business case illustration, not precise billing