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Cloud · head to head

Thanos vs HAProxy

Thanos logo

Thanos

Cloud

Highly available Prometheus with long-term object storage

From
Free
Rated
-
Full reviewWebsite
HAProxy logo

HAProxy

Cloud

High-performance TCP and HTTP load balancer

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Thanos several components — sidecar, store, querier, compactor, ruler — each with its own configuration and failure modes; HAProxy configuration syntax is dense and unforgiving, with a steep initial learning curve
  • They diverge on capability: Thanos covers Global query, HAProxy covers High throughput.

Where they differ

Only the attributes on which Thanos and HAProxy actually diverge.

Attributes where Thanos and HAProxy differ
AttributeThanosHAProxy
PlatformsKubernetes, Linux, DockerLinux, Docker, Kubernetes, Self-hosted

Identical on both: starting price (Free), pricing model (Open source, no licence fee), free tier (Yes), user rating (Not yet rated), category (Cloud).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Thanos

  • Global query
  • Object storage retention
  • Deduplication
  • Downsampling

Only in HAProxy

  • High throughput
  • Layer 4 and 7
  • Health checking
  • Rate limiting and ACLs

What people use each for

The jobs each tool is most often brought in to do.

Thanos

  • Querying metrics across many clusters or regions from one placenot HAProxy
  • Retaining metrics for years without local disk growthnot HAProxy
  • Removing the gap that appears when a single Prometheus instance restartsnot HAProxy

HAProxy

  • Load balancing at traffic levels where proxy efficiency shows up in the hardware billnot Thanos
  • Precise traffic control — rate limits, sticky sessions, complex routing rulesnot Thanos
  • TCP load balancing for databases and non-HTTP servicesnot Thanos

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Thanos

  • Several components — sidecar, store, querier, compactor, ruler — each with its own configuration and failure modes
  • The compactor is a common source of operational trouble and must not run twice against the same bucket
  • Query latency over object storage is meaningfully higher than local Prometheus
  • Object storage costs and API request charges become real at high volume

HAProxy

  • Configuration syntax is dense and unforgiving, with a steep initial learning curve
  • No automatic certificate management, unlike newer servers that treat it as default behaviour
  • The built-in stats page is basic, so real observability needs exporters and dashboards
  • A dedicated load balancer is more machinery than small deployments need

Pricing, plan by plan

Thanos

Free
  • ThanosFree
    • Full functionality
    • No usage limits
    • Community support

HAProxy

Free
  • HAProxyFree
    • Full functionality
    • No usage limits
    • Community support

Which should you pick?

Choose Thanos if

  • You need global query.
  • You want to start without paying.
  • You work on Kubernetes, Linux, Docker.
  • You also want object storage retention.
Thanos review

Choose HAProxy if

  • You need high throughput.
  • You want to start without paying.
  • You work on Linux, Docker, Kubernetes, Self-hosted.
  • You also want layer 4 and 7.
HAProxy review

Questions people ask

Is Thanos or HAProxy better?
Neither clearly leads. Thanos starts at Free and HAProxy at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Thanos or HAProxy?
Thanos starts at Free and HAProxy at Free.
Does Thanos or HAProxy run on more platforms?
Thanos runs on Kubernetes, Linux, Docker. HAProxy runs on Linux, Docker, Kubernetes, Self-hosted.
Can I use Thanos for free?
Both have a free tier, so you can try either at no cost before committing.
What is Thanos best used for?
Thanos is most often used for querying metrics across many clusters or regions from one place, retaining metrics for years without local disk growth, removing the gap that appears when a single prometheus instance restarts. Of those, querying metrics across many clusters or regions from one place and retaining metrics for years without local disk growth are not what HAProxy is typically brought in for.
What can Thanos do that HAProxy cannot?
Thanos covers Global query, Object storage retention, Deduplication, Downsampling. HAProxy covers High throughput, Layer 4 and 7, Health checking, Rate limiting and ACLs.

Answered from the vendors’ own pages

Thanos: Is Thanos free?

Yes, open source and CNCF-incubating. Costs are the object storage it uses.

HAProxy: Is HAProxy free?

Yes, the community version is open source. HAProxy Technologies sells HAProxy Enterprise separately.

Thanos: Does Thanos replace Prometheus?

No. It runs alongside existing Prometheus servers, adding global query, deduplication and long-term storage.

HAProxy: HAProxy or Nginx?

HAProxy is a specialist load balancer with deeper balancing and health-check features. Nginx also serves static content and is more approachable, which is why it is more common as a general web server.

Thanos: Thanos or VictoriaMetrics?

Thanos layers onto Prometheus using object storage and is the more established multi-cluster answer. VictoriaMetrics is a separate store aiming at lower resource use and fewer moving parts.

HAProxy: Does HAProxy handle TLS certificates automatically?

No. Certificate issuance and renewal are external, unlike Caddy where it is automatic.

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