Cortex (cortexproject/cortex) is a horizontally-scalable, highly-available, multi-tenant long-term
storage backend for What is Prometheus — accepted into CNCF in September 2018, promoted to CNCF
Incubating in August 2020, and still at that maturity level as of 2026 (not graduated). It’s the
project What is Mimir forked from, and the two now sit on opposite sides of a governance split rather
than a technical one.
Same microservice shape Mimir forked
Cortex is the origin of the distributor → ingester → (object storage) → querier / store-gateway / compactor split described in What is Mimir — Grafana Labs’ engineers built a large share of that architecture as Cortex contributors before forking their continued work into Mimir in 2022. Anyone who has operated Mimir is, mechanically, already looking at Cortex’s shape.
Timeline
| Date | Event |
|---|---|
| 2018-09-20 | Accepted into CNCF |
| 2020-08-20 | Promoted to CNCF Incubating maturity |
| 2022 | Grafana Labs forks its Cortex contributions into Mimir, steps back from co-maintaining Cortex |
| 2026 | Cortex remains CNCF Incubating (unchanged); Mimir is not itself a CNCF project |
Cortex vs. Mimir today
| Concern | Cortex | What is Mimir |
|---|---|---|
| Governance | Community-governed, CNCF Incubating project | Single-vendor (Grafana Labs) open-source project |
| CNCF standing | Formal CNCF project, subject to CNCF graduation process | Not a CNCF project at all |
| Feature velocity | Slower — smaller contributor base post-2022 fork | Faster — Grafana Labs’ primary engineering focus |
| Grafana Cloud backend | Not used — Mimir is the system of record | The actual metrics backend behind Grafana Cloud |
The practical differentiator isn’t maturity level — neither project has graduated — it’s governance: Cortex stays useful specifically for teams that want a metrics backend answerable to a CNCF technical oversight committee rather than one company’s roadmap, at the cost of a smaller contributor base and slower feature velocity than Mimir.
Where it fits next to Mimir and Thanos
| Concern | Cortex | Mimir | Thanos |
|---|---|---|---|
| CNCF status | Incubating | Not a CNCF project | Incubating |
| Origin | Independent, 2018 | Forked from Cortex, 2022 | Independent — Prometheus sidecar + object storage, not a Cortex fork |
| Governance | Community | Single-vendor | Community |
Why it’s relevant here: Mimir is already the metrics system of record in the ShipSolid Grafana Cloud stack (per What is Mimir) — this isn’t a migration candidate. It’s background for the one question that does come up in vendor conversations: “what’s the vendor-neutral fallback if we ever needed one,” and the honest answer is Cortex (community-governed CNCF project) or Thanos (independently built, also CNCF Incubating), not “there isn’t one.”
Local graph
Related notes
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 Fluent Bit
CNCF-graduated, C-written log/metrics/trace forwarder — Fluentd's lightweight sibling, the de facto node-level log-collection DaemonSet in most Kubernetes clusters, and Grafana Alloy's main incumbent competitor for that slot.
What is Jaeger
CNCF-graduated distributed tracing system built at Uber in 2015, Dapper-lineage like Zipkin before it — and, since Jaeger v2, rebuilt on top of the OpenTelemetry Collector rather than bespoke ingestion code.
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.