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It's a split decision.
Elasticsearch is a distributed search database with a RESTful HTTP API for indexing and querying structured and unstructured data, including full-text and vector search. Prometheus is an open-source metrics monitoring system built around time series, PromQL, and alerting. Choose Elasticsearch for search, analytics, and AI retrieval workloads; choose Prometheus to instrument and monitor systems and services. They address different jobs, and self-hosting either means planning for the infrastructure and operations it requires.
01Side by side
| Elasticsearch | Prometheus | |
|---|---|---|
| Pricing model | $99/month listed for hosted Standard; usage scales by resources. | Free software; infrastructure and operations remain your responsibility. |
| Free tier | No free plan listed. | Free Open Source plan; no imposed usage or seat limits. |
| Open source and licence | Open source; licence name not specified in product facts. | Apache 2.0; all components are open source. |
| Self-hosting | Self-hostable; also available in cloud and serverless deployments. | Self-hostable; servers use local storage and operate independently. |
| API and query model | RESTful HTTP API for search and analytics queries. | PromQL queries dimensional time series data. |
| Integrations | Works with Kibana, Logstash, Beats, and Elastic Agent. | Hundreds of integrations, including Kubernetes and cloud managers. |
| Deployment model | Cloud, on-premises, or serverless. | Independent servers running with local storage. |
| Limits and scaling | Usage scales by RAM-hours, storage, and availability zones. | No imposed usage limits; capacity depends on your infrastructure. |
Elasticsearch Choose Elasticsearch if
- Your application needs full-text, vector, or hybrid search.
- One engine must index structured and unstructured data.
- You want cloud, on-premises, or serverless deployment options.
Prometheus Choose Prometheus if
- You need metrics monitoring and PromQL-based alerting.
- You want open-source software under the Apache 2.0 licence.
- You prefer independent servers with local storage and no usage fees.
02Pricing at real usage
Elastic Cloud Hosted (Standard) is listed at $99 per month and includes 120 GB of storage and two availability zones. There is no free plan in the listed pricing. Elastic says usage scales by RAM-hours, storage, and zones; users are unlimited, while seat limits are not published. The annual-billing price is not published, though prepaid consumption contracts are available through sales.
Prometheus costs $0 per month under its Open Source plan, with no imposed usage or seat limits. That is the software price, not the cost of running it: you provide the infrastructure and handle operations. Its independent servers use local storage, so capacity and retention planning are part of deployment. For a budget comparison, estimate Elastic usage against RAM-hours, storage, and zones; for Prometheus, account for the machines and operating work needed for your monitoring workload.
03API, SDKs and integration
Elasticsearch exposes a RESTful HTTP API for storing, indexing, and querying data. Its search capabilities include full-text, vector, and hybrid search, with real-time analytics and retrieval for applications that need to provide context to LLMs. In the Elastic Stack, it works with Kibana, Logstash, Beats, and Elastic Agent. The product facts do not name SDK languages, so check Elastic's current API documentation for the clients and language versions your codebase requires.
Prometheus is centered on its dimensional time-series model and PromQL, which queries, correlates, and transforms metrics. PromQL also defines alerting rules; Alertmanager handles notifications and silencing. Official and community instrumentation libraries cover most major languages, but specific languages are not named here. Prometheus also has hundreds of official and community integrations, including Kubernetes and other cloud and container managers. Its servers operate independently and rely on local storage.
04Open source, self-hosting and lock-in
Both products are self-hostable. Elasticsearch is described as open source and can run in the cloud, on-premises, or serverless. Its licence name is not specified in the product facts, so confirm the applicable terms before choosing a deployment. Prometheus is 100% open source, and its components use the Apache 2.0 licence.
These systems model different data, so migration is not a direct swap. Elasticsearch indexes structured and unstructured data for search; Prometheus stores dimensional metrics queried with PromQL. Moving between them can mean changing how you instrument services, structure data, write queries, and define alerts. The product details do not establish data-export formats or migration tooling. Before committing, verify export paths and test how your indexes, metric labels, queries, and alert rules would move to the systems you plan to use.
Questions people ask
What is Prometheus used for in Kubernetes?
Prometheus collects and queries metrics for monitoring applications, systems, and services. Its Kubernetes and cloud-manager integrations can discover and monitor services, while PromQL supports queries and alerting rules. Alertmanager handles notifications and silencing.
Is Prometheus an alternative to Elasticsearch?
They overlap as data systems but serve different primary jobs. Prometheus is designed to collect and query time-series metrics and define alerts. Elasticsearch indexes and searches structured and unstructured data, including full-text and vector search. Choose based on the workload, not the product names.
What does ELK stand for?
ELK refers to Elasticsearch, Logstash, and Kibana. Elasticsearch is the search database; Logstash and Kibana are part of the Elastic Stack alongside Beats and Elastic Agent. The stack integrates ingestion, search, and visualization components.
Can Prometheus replace Elasticsearch for logs and search?
Prometheus is a metrics monitoring system, not a full-text search database. Its PromQL queries time series, while Elasticsearch supports full-text search over stored data and indexes structured and unstructured data. For logs and search, Elasticsearch fits that workload more directly.