SLAs · Performance Testing 101
SLAs in Performance Testing
Service Level Agreements define clear pass/fail criteria for performance tests — ensuring expectations are aligned, results are measurable, and performance is predictable.
An SLA (Service Level Agreement) is a mutually agreed performance target between the client and the performance testing team. It defines what acceptable performance looks like — and when the system fails the test.
SLAs Help Answer
- What is acceptable performance?
- When does the system fail the test?
- Which metrics must stay within limits?
Why SLAs Matter
- Performance is predictable
- Expectations are aligned
- Results are not subjective
- Pass/fail is measurable
📏 Across entire test run (e.g., 1-hour test)
⏱️ Across time intervals (e.g., every 1 minute)
01
Avg Response Time per Interval
⏱️
Checks average response time of a transaction every minute (or other interval). If any interval exceeds the threshold → SLA FAIL.
SLA Threshold
Checkout Avg RT < 800 ms / minute
✓ 620 ms
✗ 950 ms
→ Any minute > 800ms = FAIL
02
Errors per Second per Interval
⚠️
Measures how many errors occur every second during the test. A sudden spike in errors triggers SLA failure.
SLA Threshold
Error Rate < 1 error/sec
✓ 0.3 err/s
✗ 5 err/s
→ Spike above 1 = FAIL
Total number of requests the system should process in the entire test run. Measures overall capacity delivery.
SLA Threshold (1-Hour Test)
Total Hits ≥ 200,000
✓ 215K
✗ 150K
→ Below 200K = FAIL
04
Avg Hits/sec per Run
📈
Average number of requests the system handles each second across the whole test. Measures sustained throughput.
SLA Threshold
Avg Hits ≥ 100 hits/sec
✓ 112 h/s
✗ 75 h/s
→ Below 100 = FAIL
05
Total Throughput (bytes) per Run
💾
Total amount of data processed (sent + received) during the full test. Validates data capacity.
SLA Threshold (1-Hour Test)
Total Throughput ≥ 20 GB
✓ 23 GB
✗ 12 GB
→ Below 20 GB = FAIL
06
Avg Throughput (bytes/sec) per Run
🌊
Average data transfer rate across the entire test. Ensures consistent bandwidth and data flow.
SLA Threshold
Avg Throughput ≥ 500 KB/sec
✓ 580 KB/s
✗ 300 KB/s
→ Below 500 = FAIL
∑
Quick Reference Summary
| SLA Type | Meaning | Threshold Example |
|---|
| Avg Response Time / Interval | RT must stay within limit every minute | < 800 ms / min |
| Errors per Second | Error rate threshold per interval | < 1 error/sec |
| Total Hits per Run | Total requests in entire test | ≥ 200,000 hits |
| Avg Hits/sec | Avg requests per second | ≥ 100 hits/sec |
| Total Throughput (bytes) | Total data processed | ≥ 20 GB |
| Avg Throughput (bytes/sec) | Data rate per second | ≥ 500 KB/sec |