13.2 Golden signals — four questions in plain English
Google's SRE book popularised four golden signals for user-facing services. Learn the idea; you do not need to memorise every SRE chapter.
| Signal | Plain question | badge API example |
|---|---|---|
| Latency | How long do requests take? | /badge p95 response time |
| Traffic | How much demand? | Requests per second |
| Errors | How often do we fail? | HTTP 5xx rate |
| Saturation | How "full" are we? | CPU %, disk %, connection pool |
Host metrics (this chapter's lab focus) sit mostly under saturation and help explain why latency or errors climbed. Application golden signals often need app instrumentation or a reverse proxy — later you will combine both.
Tiny story. Priya sees latency climb at 12:40. Traffic is normal. Errors are low. Disk is 98% full — logs could not rotate cleanly and the API started stuttering. Saturation explained the lunch mystery.
Ravindra Bagale's Tip
Khup students fakt CPU baghtat. Disk full + inode full + RAM pressure — te pan saturation. df -h aani df -i lab madhe habit banva. Dhyan rakho!