Cortex

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What Cortex is

Cortex is an open source system for keeping Prometheus and OpenTelemetry metrics over the long term. It accepts Prometheus samples through remote_write and can ingest data through OTLP. Metrics are queried with PromQL, including by Grafana, and an HTTP API supports pushing and querying time series data as well as operating the cluster. Cortex can run on one machine for development and testing, or as separate microservices for production. Clustered deployments can spread work across machines and replicate data between them, while tenant isolation keeps data and queries from independent Prometheus sources separate. For long-term storage, Cortex supports S3, Google Cloud Storage, OpenStack Swift, and Microsoft Azure. It also supports retention policies, TLS between components, server-side encryption for supported storage paths, and distributed tracing with Jaeger or OpenTelemetry. Production microservices can run as separate services in Kubernetes. Cortex is self-hosted, and its release artifacts regularly target Linux and macOS; other operating systems may work from source. The project began in 2016 and is licensed under Apache License 2.0.

Who it suits

Cortex suits operators who need scalable, self-hosted long-term storage for Prometheus or OpenTelemetry metrics and want to query with PromQL. It is also a fit for deployments that need tenant separation, storage integrations, or a choice between a single process and a Kubernetes microservices setup.

What it does well

Scales across machines and can replicate data between them.
Accepts Prometheus remote_write and OpenTelemetry Protocol data.
Queries metrics with PromQL.
Supports S3, Google Cloud Storage, Swift, and Azure storage.
Offers retention policies and tenant isolation.
Apache License 2.0 open source project.

What to know first

Authentication and authorization must be added externally, typically through a reverse proxy.
Tenant headers require an additional protection layer for the installation.
SQL is not supported.
Windows is not a regular supported release target.

Getting started

Visit the Cortex website.
Choose Linux or macOS release artifacts, or build from source for other operating systems.
Run a single binary for development and testing, or deploy microservices for production.
For a production microservices deployment, run the separate components in Kubernetes.
Configure external authentication and authorization, typically through a reverse proxy.
Send Prometheus samples through remote_write or ingest through OTLP, then query with PromQL.

Verdict

Choose Cortex if you can operate your own metrics storage and need PromQL queries, horizontal scaling, or long-term storage integrations. Look elsewhere if you need SQL or expect authentication and authorization to be built into Cortex without external configuration.

Questions

What does Cortex cost?

Cortex is free and open source under the Apache License 2.0.

Where can I run Cortex?

Cortex is self-hosted. Regular release artifacts target Linux and macOS; other operating systems may work from source.

Which data formats and query language does Cortex support?

It ingests Prometheus remote_write and OpenTelemetry Protocol data. PromQL is used to query metrics.

Does Cortex support SQL?

No. SQL support is listed as unavailable.

How does Cortex handle authentication?

Authentication and authorization are configured externally, typically through a reverse proxy. Its components trust the X-Scope-OrgID tenant header, so an additional protection layer is needed.

Where can users get project support?

The project directs users to its CNCF Slack channel, GitHub issues, and [email protected].

Facts from Cortex's own pages

API: Cortex exposes an HTTP API for pushing and querying time-series data and operating the cluster. · cortexmetrics.io, 9 Oct 2026
Deployment modes: Cortex can run as a single binary for learning, development, and testing, or as independent microservices for production deployments. · cortexmetrics.io, 9 Oct 2026
Encryption: Cortex supports TLS between its components and S3 server-side encryption using SSE-S3 or SSE-KMS for supported storage paths. · cortexmetrics.io, 8 Oct 2026
Founded: 2016 · cortexmetrics.io, 28 Sept 2026
HTTP API: Cortex exposes an HTTP API for pushing and querying time series data and operating the cluster. · cortexmetrics.io, 8 Oct 2026
Kubernetes: The production-style microservices setup runs Cortex components as separate services in Kubernetes. · cortexmetrics.io, 8 Oct 2026
License: Cortex is an open-source project licensed under Apache License 2.0. · cortexmetrics.io, 9 Oct 2026
Metrics and queries: Prometheus sends metrics to Cortex using remote_write, and Grafana can query Cortex using PromQL. · cortexmetrics.io, 9 Oct 2026
Purpose: Cortex is a horizontally scalable, highly available, multi-tenant long-term storage solution for Prometheus and OpenTelemetry metrics. · cortexmetrics.io, 9 Oct 2026
Query and ingestion: Prometheus sends samples to Cortex through its remote write API, and users query metrics with PromQL. · cortexmetrics.io, 8 Oct 2026
Scalability and availability: Cortex can run across multiple machines, and clustered deployments can replicate data between machines. · cortexmetrics.io, 9 Oct 2026
Scaling and availability: Cortex can run across multiple machines in a cluster and replicate data between machines. · cortexmetrics.io, 8 Oct 2026
Security audit: A third-party audit reported seven vulnerabilities, and the project says fixes shipped in Cortex v1.21.1, released June 4, 2026. · cortexmetrics.io, 9 Oct 2026
Security boundary: Cortex requires authentication and authorization to be configured externally, typically through a reverse proxy. · cortexmetrics.io, 8 Oct 2026
Security configuration: Cortex supports TLS between its components, while authentication and authorization are typically added through a reverse proxy. · cortexmetrics.io, 9 Oct 2026
Storage integrations: Cortex supports S3, Google Cloud Storage, Swift, and Microsoft Azure for long-term metric storage. · cortexmetrics.io, 9 Oct 2026
Support: The project directs users to its CNCF Slack channel, GitHub issues, and the cortex-users mailing list for questions. · cortexmetrics.io, 9 Oct 2026
Supported release targets: Regular release artifacts include Linux and macOS binaries; other operating systems may work from source but are not regular supported release targets. · cortexmetrics.io, 9 Oct 2026
Tenant access limitation: Cortex components trust the X-Scope-OrgID tenant header, so the security guide says an additional protection layer is needed to guard the installation. · cortexmetrics.io, 8 Oct 2026
Tenant isolation: Cortex can isolate data and queries from multiple independent Prometheus sources in one cluster. · cortexmetrics.io, 9 Oct 2026
Tracing: Cortex supports distributed tracing using Jaeger or OpenTelemetry. · cortexmetrics.io, 8 Oct 2026
What it does: Cortex is a horizontally scalable, highly available, multi-tenant, long-term storage solution for Prometheus and OpenTelemetry metrics. · cortexmetrics.io, 8 Oct 2026

Where Cortex stands on Freedom251

Time-Series Databases#11 of 36