slo-implementation

# SLO Implementation

Framework for defining and implementing Service Level Indicators (SLIs), Service Level Objectives (SLOs), and error budgets.

## Purpose

Implement measurable reliability targets using SLIs, SLOs, and error budgets to balance reliability with innovation velocity.

## When to Use

- Define service reliability targets
- Measure user-perceived reliability
- Implement error budgets
- Create SLO-based alerts
- Track reliability goals

## SLI/SLO/SLA Hierarchy

```
SLA (Service Level Agreement)
  ↓ Contract with customers
SLO (Service Level Objective)
  ↓ Internal reliability target
SLI (Service Level Indicator)
  ↓ Actual measurement
```

## Defining SLIs

### Common SLI Types

#### 1. Availability SLI
```promql
# Successful requests / Total requests
sum(rate(http_requests_total{status!~"5.."}[28d]))
/
sum(rate(http_requests_total[28d]))
```

#### 2. Latency SLI
```promql
# Requests below latency threshold / Total requests
sum(rate(http_request_duration_seconds_bucket{le="0.5"}[28d]))
/
sum(rate(http_request_duration_seconds_count[28d]))
```

#### 3. Durability SLI
```
# Successful writes / Total writes
sum(storage_writes_successful_total)
/
sum(storage_writes_total)
```

**Reference:** See `references/slo-definitions.md`

## Setting SLO Targets

### Availability SLO Examples

| SLO % | Downtime/Month | Downtime/Year |
|-------|----------------|---------------|
| 99%   | 7.2 hours      | 3.65 days     |
| 99.9% | 43.2 minutes   | 8.76 hours    |
| 99.95%| 21.6 minutes   | 4.38 hours    |
| 99.99%| 4.32 minutes   | 52.56 minutes |

### Choose Appropriate SLOs

**Consider:**
- User expectations
- Business requirements
- Current performance
- Cost of reliability
- Competitor benchmarks

**Example SLOs:**
```yaml
slos:
  - name: api_availability
    target: 99.9
    window: 28d
    sli: |
      sum(rate(http_requests_total{status!~"5.."}[28d]))
      /
      sum(rate(http_requests_total[28d]))

  - name: api_latency_p95
    target: 99
    window: 28d