Defining performance terminology
Concept · Chapter 10
Why the vocabulary matters
Section titled “Why the vocabulary matters”Architects need precise terms to specify, measure, and discuss performance. These terms are frequently confused (especially latency vs. response time), so pin them down before optimizing.
The terms
Section titled “The terms”| Term | Definition | Notes / units |
|---|---|---|
| Latency | Time (delay) to send information from source to destination — “time on the wire.” | Usually ms. Affected by network hardware, connection type, distance, congestion. |
| Throughput | Work items per unit time. | Network: data moved per time (bps, Mbps, Gbps). App logic: e.g. transactions/second. |
| Bandwidth | The maximum possible throughput for a given logical/physical path. | A bit-rate ceiling. |
| Processing time | Time for the system to process a request, excluding network latency. | Sometimes split into server vs. client processing time. Affected by code, external software, hardware. |
| Response time | Total time from user request to user receiving the response. | = network latency + processing time. Not a synonym for latency. |
| Workload | Amount of computational processing a machine has at a given time. | Consumes processor capacity. Types: CPU, memory, I/O, database. Track it to predict peak loads. |
| Utilization | % of time a resource is in use vs. total time available. | E.g. CPU busy 45s of a 60s window = 75%. Measure CPU, memory, disk. As utilization nears max throughput, response times rise. |
Key distinctions to remember
Section titled “Key distinctions to remember”- Latency ≠ response time. Response time bundles both the wire time (latency) and the compute time (processing time).
- Bandwidth ≠ throughput. Bandwidth is the theoretical ceiling; throughput is what you actually achieve.
- Last-mile latency: a large share of total latency often occurs between the home/office and the ISP — the first or last few hops can dominate even for cross-country/global traffic.
- Utilization is an early warning: climbing utilization foreshadows rising response times before hard limits are hit.
Related concepts
Section titled “Related concepts”- The importance of performance
- Taking a systematic approach to performance improvement
- Improving web application performance
Citations
Section titled “Citations”- Software Architect’s Handbook (Packt, 2018), Ch.10 “Defining performance terminology”, pp. 740-747.