USE Method
USE — Utilisation, Saturation, Errors — is Brendan Gregg's framework for diagnosing resource-level health (CPU, memory, disk, network). Utilisation is the percent of time the resource was busy; Saturation is the queue depth waiting on it; Errors is the count of operations that failed. RED tells you *that* a service is unhealthy; USE tells you *which resource* is to blame.
Concepts that travel with this one.
Architecture rarely lives in isolation — these are the terms that come up in the same conversation.
RED Method
RED stands for Rate, Errors, Duration — the three service-level signals every request-driven service should emit. Rate is requests per second; Errors is the fraction that fail; Duration is the latency distribution. A RED dashboard answers 'is this service healthy right now' in under five seconds. TantraDev ships a RED dashboard per service before the first cutover on every cloud engagement.
Observability
Observability is the property of a system that lets you answer questions about its behaviour from its outputs alone, without shipping new code. The three signals are metrics, logs, and traces; the operational test is whether an on-call engineer can root-cause a novel incident from the existing dashboards. Observability is in the data model from week one on every TantraDev engagement, not bolted on after launch.
Golden Signals
The Four Golden Signals, from Google's SRE book, are Latency, Traffic, Errors, and Saturation — the minimum set of signals to monitor on any user-facing service. They overlap with RED and USE but stay user-facing in framing: a latency spike that customers feel matters more than CPU saturation that they don't. TantraDev alert policies are golden-signal-shaped.
Building a system where USE Method is the load-bearing decision?
30 minutes on the phone, one page in your inbox — what to build, what to skip, what it will cost. You keep the audit even if we are not the right fit.