Which metrics are used to measure system reliability in MDC3?

• A. Number of developers
• B. Time to publish a release
• C. Uptime, MTTR, MTBF, error rates, and SLO achievement
• D. Number of features added

Answer: (C)

Measuring system reliability focuses on how long the system stays available, how quickly it recovers from problems, and how often errors occur. The best way to quantify that is to look at uptime (the portion of time the system is operational), MTTR (how long it takes to restore service after an incident), MTBF (the average time between failures), error rates (how often errors happen), and whether the service meets its stated reliability targets (SLO achievement). These metrics together capture both the frequency and impact of outages and the efficiency of recovery, which are the key indicators of reliability.

The other options don’t directly reflect reliability. The number of developers describes team size, not how the system behaves; time to publish a release measures delivery speed, not how stable or available the system is; the number of features added concerns scope and functionality, not how reliably the system runs.