# Observability
All Observability notes →What is Cortex (cortexproject)
CNCF Incubating, horizontally-scalable multi-tenant long-term storage for Prometheus — the project Grafana Mimir forked from in 2022, still maintained as the vendor-neutral, community-governed alternative once Grafana Labs redirected engineering effort to Mimir.
What is Mimir
Grafana Labs' horizontally-scalable, multi-tenant long-term storage for Prometheus metrics — the 2022 successor to Cortex, and the actual system serving every PromQL query and remote-write in a Grafana Cloud metrics stack.
What is Prometheus
CNCF's second graduated project (2018) — the pull-based metrics monitoring system and query language (PromQL) that defined the exposition format nearly every metrics tool now speaks, and the API that Grafana Mimir scales out horizontally.
What is StatsD
Etsy's 2011 UDP-based metrics protocol and daemon — the simplest possible fire-and-forget instrumentation format, superseded as a client API by OTel/Prometheus but still alive everywhere as a compatibility ingestion shim.
What is Cardinality (in observability)
The number of unique time series (or unique log/trace label combinations) a metric produces — the single biggest driver of ingest cost and query latency in Prometheus-family backends (Mimir, Cortex, Thanos), and the reason unbounded labels are a production incident waiting to happen.
What is Telegraf
InfluxData's plugin-driven metrics/events/logs collection agent — 300+ input/output plugins, written in Go, single static binary — the collector layer in the InfluxDB (TICK-stack-descendant) ecosystem, comparable in role to Grafana Alloy.
1 — Time Series Fundamentals
Covers the time-series data model — series identity, sample resolution, and the write/query tradeoffs baked into that model.
2 — Metric Types
Distinguishes counter, gauge, histogram, and summary semantics and the aggregation rules each type permits or forbids.
4 — Cardinality Management
Covers estimating and bounding active series count before a label change ships, and the incident patterns an unbounded label causes.
6 — Recording Rules
Covers pre-computing expensive PromQL expressions into new series to keep dashboard and alert queries fast at scale.
# Internal Developer Platforms
All Internal Developer Platforms notes →1 — Adoption Metrics
Adoption metrics, active users, service coverage, template usage, self-service rate, that show whether the platform is actually being used, not just built.
2 — Productivity Metrics
Productivity metrics, time to first deployment, lead time, developer wait time, deployment velocity, the platform is ultimately accountable for moving.
3 — Platform Reliability Metrics
Reliability metrics for the platform's own APIs and workflows: availability, latency, workflow success rate, provisioning success.
4 — Developer Satisfaction
Developer satisfaction measurement, surveys, NPS, structured feedback loops, as the qualitative complement to the quantitative metrics above.