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Esper

espertech.com

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Spec score 8.7 #4 of 26 in Stream Analytics Software

What it is

Esper is a language, compiler, and runtime for complex event processing and streaming analytics in Java and .NET. Its Event Processing Language extends SQL with expressions over events and time. The compiler turns EPL into bytecode that can be packaged in JAR files. Esper and NEsper embed inside Java or .NET processes rather than running as standalone servers. The in-memory runtime is described as memory-efficient and low-latency and does not require external storage or services. Adapters handle CSV, JMS, HTTP, Kafka, database, and socket input and output, with JMX metrics exposure. Queries can join event streams with web services and relational databases through SQL-query or method-invocation joins. Esper Enterprise Edition adds scale-out architecture with elastic scaling, load balancing, fault tolerance, and multi-datacenter support using Apache Kafka and Apache Zookeeper. Listed uses include business-process monitoring, financial applications such as fraud detection, network and application monitoring, and sensor networks. Esper 9.0.0 is listed under GNU GPL (GPL v2); commercial redistribution licenses are available. Production support has Bronze, Silver, and Gold levels, plus a Developer Seat for how-to questions.

Spec sheet

What it does
Esper is a language, compiler and runtime for complex event processing and streaming analytics.Read 15 Oct 2026 · espertech.com
Purpose
Esper is a language, compiler and runtime for complex event processing and streaming analytics, available for Java and .NET.Read 3 Oct 2026 · espertech.com
Integrations
The feature list names CSV, JMS, HTTP, Kafka, database and socket input/output adapters, and JMX metrics exposure.Read 3 Oct 2026 · espertech.com
Support
Commercial support is offered on 24x7 or 8x5 schedules through phone, email or a web portal.Read 15 Oct 2026 · static.espertech.com
Headquarters
EsperTech lists a mailing address in Wayne, New Jersey, USA.Read 15 Oct 2026 · espertech.com
Founded
Esper is documented as created in 2006, with its first public release in early 2006.Read 15 Oct 2026 · en.wikipedia.org
API documentation
Official documentation provides separate JavaDoc for the API, compiler, runtime, common modules, Avro and EsperIO.Read 15 Oct 2026 · espertech.com
Commercial licensing
EsperTech offers EULA and OEM licenses that remove GPL copyleft obligations, with redistribution rights for OEMs.Read 15 Oct 2026 · static.espertech.com
Company legal name
The maker identifies itself as EsperTech Inc.Read 15 Oct 2026 · espertech.com
Compilation
The Esper compiler compiles EPL into bytecode that can be packaged in JAR files for distribution and execution.Read 3 Oct 2026 · espertech.com
Continuous processing
The engine stores queries and evaluates incoming events continuously instead of polling stored records.Read 15 Oct 2026 · esper.espertech.com
Current release
The documentation page identifies Esper and EsperIO 9.0.0 as the current release.Read 3 Oct 2026 · espertech.com
Deployment model
Esper and NEsper are embeddable components for Java and .NET processes rather than standalone servers.Read 3 Oct 2026 · espertech.com
Developer tooling
EsperTech provides a free Visual Studio Code extension and EPL language server.Read 15 Oct 2026 · espertech.com
Documentation depth
EsperTech publishes reference manuals, API JavaDocs, examples, training material and a knowledge base across many releases.Read 15 Oct 2026 · espertech.com
Downloads
Core downloads are public, while Enterprise Edition and EsperHA downloads require registration or login.Read 15 Oct 2026 · espertech.com
Embedding
Esper is designed to run inside Java or .NET processes and does not require external services or storage.Read 15 Oct 2026 · espertech.com
Enterprise security
Esper Enterprise Edition says EsperHQ and EsperJMX can access CEP engines remotely over secured connections with user credentials.Read 3 Oct 2026 · espertech.com
Event formats
Supported event representations include Java objects, maps, JSON, XML, object arrays and Avro.Read 15 Oct 2026 · espertech.com
Event language
Its Event Processing Language (EPL) implements and extends SQL for expressions over events and time.Read 3 Oct 2026 · espertech.com
Event Processing Language
Its EPL language extends SQL-style querying with event-time and stream-processing operations.Read 15 Oct 2026 · espertech.com
Extension APIs
Extension points include plug-in loaders, data-flow operators, virtual data windows, method invocation and external service calls.Read 15 Oct 2026 · esper.espertech.com
External data
Esper supports joining external data, including web services, relational databases through SQL-query joins and method invocation joins.Read 3 Oct 2026 · espertech.com
Independent assessment
Bloor Research describes Esper as an early open-source CEP engine and says commercial licenses are needed for OEM use.Read 15 Oct 2026 · bloorresearch.com
Independent deployment finding
Bloor reports that Esper can run as an embedded component, self-contained stack or Docker container across edge, on-premises and cloud environments.Read 15 Oct 2026 · bloorresearch.com
Independent Kafka finding
Bloor reports that Enterprise Edition can add instances dynamically and use Kafka-based failover when an instance goes down.Read 15 Oct 2026 · bloorresearch.com
Independent technical evidence
A peer-reviewed study selected Esper for reported performance, operator versatility and technological maturity when integrating CEP with message brokers.Read 15 Oct 2026 · pmc.ncbi.nlm.nih.gov
Kafka integration
EsperIO includes Kafka input and output adapters, while Enterprise Edition uses Kafka in its distributed architecture.Read 15 Oct 2026 · esper.espertech.com
Licence
The open-source Esper and NEsper code is released under the GNU GPL version 2.Read 15 Oct 2026 · github.com
Licensing
The downloads page lists Esper 9.0.0 under GNU GPL (GPL v2), and EsperTech says it offers commercial redistribution licenses for companies incorporating Esper or NEsper.Read 3 Oct 2026 · espertech.com
Limit: GPL terms
EsperTech's licensing comparison says GPL distribution can impose viral copyleft and that the GPL package has no high-availability or enterprise add-ons.Read 15 Oct 2026 · static.espertech.com
Limit: Kafka adapter
The documented EsperIO Kafka adapter is a local reader and is not intended for coordinated multi-server use.Read 15 Oct 2026 · esper.espertech.com
Limit: product scope
Bloor characterizes EsperTech products as components of a larger stack rather than a complete one-stop solution.Read 15 Oct 2026 · bloorresearch.com
Notable news
Esper 9.0.0 was released on April 26, 2024 and introduced the Java 17 requirement.Read 15 Oct 2026 · espertech.com
Other integrations
EsperIO documentation covers AMQP, JMS, HTTP, sockets, files, JDBC databases and XML or JSON output.Read 15 Oct 2026 · esper.espertech.com
Pattern detection
Esper supports state-machine event patterns that match sequences, absences and time-based relationships.Read 15 Oct 2026 · esper.espertech.com
Praise: developer experience
A Bloor customer quote praises the combination of flexibility, ease of development and high throughput.Read 15 Oct 2026 · bloorresearch.com
Praise: documentation
Bloor says EsperTech emphasizes extensive documentation and self-help resources.Read 15 Oct 2026 · bloorresearch.com
Rating on TrustRadius
Esper (open source) is rated 0 out of 10 from 0 reviews.Read 15 Oct 2026 · trustradius.com
Rating on TrustRadius Enterprise
Esper Enterprise Edition is rated 0 out of 10 from 0 reviews.Read 15 Oct 2026 · trustradius.com
Runtime
The runtime is an in-memory streaming engine that the site describes as memory-efficient and low-latency, and says does not require external storage or services.Read 3 Oct 2026 · espertech.com
Runtime deployment
Compiled EPL becomes bytecode that can be packaged and executed by the Esper runtime.Read 15 Oct 2026 · espertech.com
Scale
Esper’s runtime has a horizontal scale-out architecture with elastic scaling, load balancing, fault tolerance and multi-datacenter support, built on Apache Kafka and Apache Zookeeper in Esper Enterprise Edition.Read 3 Oct 2026 · espertech.com
Scale-out
The enterprise runtime offers linear and elastic horizontal scaling, load balancing, dynamic discovery and replication.Read 15 Oct 2026 · espertech.com
Security feature
Enterprise Edition states that EsperHQ and JMX can access engines remotely over secured connections with user credentials.Read 15 Oct 2026 · espertech.com
Stream analytics
EPL provides stream windows, aggregations, joins and other analysis functions for event streams.Read 15 Oct 2026 · esper.espertech.com
Support limitation
Developer Seat support answers how-to questions and does not fix software bugs or provide training.Read 3 Oct 2026 · espertech.com
System requirement
Esper 9.0.0 requires Java 17 or newer; earlier 8.x releases support Java 8 or newer.Read 15 Oct 2026 · espertech.com
Target use cases
The site lists business process monitoring, financial applications such as fraud detection, network and application monitoring, and sensor network applications as typical uses.Read 3 Oct 2026 · espertech.com

Plans and prices

Esper 9.0.0 Free GNU GPL (GPL v2) Read 3 Oct 2026 · espertech.com
Esper Open Source Free GPLv2 license · Java/JVM and .NET/NEsper · software supplied as-is Read 15 Oct 2026 · github.com
Esper Enterprise Edition Priced on request closed-source commercial product · horizontal scaling · REST services · GUI · JDBC/JMX · commercial support Read 15 Oct 2026 · espertech.com
EsperHA Priced on request high-availability add-on · state resilience · fast recovery · enterprise support Read 15 Oct 2026 · static.espertech.com
Esper support Priced on request per year and per instance or per seat Production support: Bronze, Silver, Gold · Development support: Developer Seat Read 3 Oct 2026 · espertech.com

Every Esper plan and price →

Strong points and limits

Strong points

  • EPL extends SQL for event and time expressions
  • Embeds in Java and .NET processes
  • Includes multiple input and output adapters
  • Supports external-data joins
  • GPL-licensed 9.0.0 release available

Limits

  • Esper is an embeddable component, not a standalone server
  • Enterprise scale-out features are edition-specific
  • Developer Seat excludes bug fixing and training
  • Commercial redistribution licensing may be needed

Who it suits

Esper suits Java and .NET developers embedding event processing into applications that analyze streams and time-based conditions. It also targets the listed monitoring, financial, and sensor-network use cases.

Verdict

Esper combines an SQL-derived event language, embeddable runtime, integrations, and optional enterprise scaling. Decide between the GPL release, commercial redistribution terms, and support levels based on deployment and assistance needs.

Where Specifiction places it

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