Rule Engine Microservice For Scalable Systems

Know how your organization can develop scalable and modular systems by using various features of the rules engine microservice.

Rule Engine Microservice For Scalable Systems

Prabhat Gupta

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Rule Engine Microservice For Scalable SystemsRule Engine Microservice For Scalable Systems
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Rule engine microservice has become an important aspect of modern software architecture and in the area of microservices. Companies can directly build a scalable system with microservices. Developers can develop an application by externalizing and managing business rules efficiently. 

As most organizations are moving towards a microservices architecture, rule engine microservices have become an important part of building a scalable software system. Microservices have modular and independently deployable components and provide a framework for developing complex applications that can evolve and scale properly. In this article, let us learn about rule engine microservices, modern microservices architecture, implementation and best practices.

What is a Rule Engine Microservice?

A rule engine microservice is a specialized component within a microservices architecture that is responsible for executing and managing business rules in a modular and scalable manner. 

Business rules are specific predefined statements that define the logic behind decision processes within a software application. These rules can be simple conditional statements or complex algorithms that determine specific actions or outcomes based on the input data.

The primary purpose of a rule engine microservice is to externalize and centralize an application's business rules, which promotes and allows for more flexibility, adaptability, and maintainability. Instead of embedding business rules directly into the core application code, which can make the system rigid and less responsive to changes, the Rule Engine Microservice provides a standalone environment to define, modify, and execute these rules.

Advantages of Microservices:

Microservices offer several advantages that contribute to their popularity in modern software development. With or without microservices Nected has a performant architecture which gives developers ease of development and deployment. Below are the merits of microservices architecture. 

  • Scalability: Services can be individually scaled based on demand. Resource utilization and cost estimation should be handled with utmost care. 
  • Fault Isolation: Issues in one service do not necessarily impact others, promoting fault isolation. 
  • Ease of Deployment: Microservices support continuous delivery and deployment. Changes to one service can be made and deployed without affecting the entire application, leading to faster release cycles.

Key Characteristics of Microservices Rule Engine

The Key characteristics of a Rule Engine Microservice include:

  • Separation of Concerns: By isolating business rules from the core application logic, Rule engine microservices promote separation of concerns, as shown in the image above. 
  • Scalability: In a microservices architecture, each microservice is typically a self-contained unit that can be scaled independently. Rule engine microservices follow the same principle, allowing organizations to scale the rule-processing capability separately from other application components.
  • Adaptability to Change: Business rules often need to be adapted to changing business requirements, market conditions, or regulatory standards. Rule engine microservices enable organizations to respond quickly to these changes, as modifications to rules can be made without affecting the entire application.
  • Centralized Rule Management: Rule engine microservices provide a centralized platform for managing and versioning business rules. The centralized approach offered by the architecture makes it easier to maintain and track the changes. 

Rules Engine Microservices Architecture

The microservices rules engine architecture combines the characteristics of microservices with the intelligence of a rule engine. The components, communication protocols and design patterns contribute to this architecture in managing and executing business rules across different software systems. The below screenshot depicts a high-level microservices architecture of an alerts and notifications system.

In this section let us see about the core components, integration, protocols and other concepts like monitoring and logging. 

Key Components in the Rules Engine Microservice Architecture

The architecture mainly has three components which are the rules engine, API Layer and rules repository. Let us see each component in detail.

Rule Engine:

  • The rule engine is the main part of the microservices rules engine architecture. It functions as the central point for data intelligence. 
  • It executes business rules based on the incoming data. This component is made to adapt and respond to dynamic business scenarios. 

API Layer:

  • The API Layer is the communication gateway. It gives interaction between microservices and rules engines. 
  • It handles the evaluation of rules, data submissions, and retrieval of results. It also maintains the entire system architecture for collaboration between microservices. 

Rule Repository:

  • The rule repository is the storage backbone. It is responsible for managing business rules in the architecture. 
  • With the support for versioning, it handles the diverse rule sets that allow for easy retrieval by the rule engine. 

Nected has a very simple GUI that allows you to develop a rules engine suitable for your organization’s needs. Nected's Rule Engine supports database connectors and REST API integrations. It can connect to internal databases or external APIs like Zoho.

Integration Process of Microservices Rule Engine

Below are the steps in identifying and integrating the microservices rules engine in your organization.

1. Microservices Identification:  Identify the functions that each microservice will possess. Also, determine each microservice's input data and output data within the larger system. 

2. API Definition:  Create proper APIs to make communication between microservices and the rule engine. Define the methods, endpoints and data formats that microservices will use to send and receive the data for rule processing. 

3. Rule Engine Configuration:  Set up the rules engine to respond to queries from microservices. Specify the APIs and expose endpoints and also make sure the rule engine has the tools to carry out business rules depending on input. 

4. Microservices Development:  Develop individual microservices by incorporating the APIs for communication with Rule Engine. Implement the correct logic in each microservice before sending it to the rule engine for rule assessment. 

5. API Integration Testing:  Conduct testing of APIs to check the communication between microservices and the rules engine. Also, check the data submission and result retrieval. 

6. Service Orchestrator Implementation: Develop the service orchestrator component for coordinating the flow of data and requests between microservices and the Rule Engine. Implement sequencing logic to order the rules execution.

Image: Logic sequencing for rules execution in Nected

7. Data Flow Coordination: Integrate mechanisms within the Service Orchestrator to coordinate the flow of data between microservices and the Rule Engine. Address scenarios where microservices depend on the results of other services to maintain data consistency.

8. Deployment and Monitoring: Deploy the integrated microservices architecture and rule engine into the production environment. Make use of some monitoring tools to track the performance, and identify bottlenecks. 

9. Scalability Considerations: Plan for scalability by designing the integration to accommodate the addition of new microservices or changes in business rules. The scalability must be observed in a scalable fashion. 

10. Documentation: Documenting the APIs, integration processes, and any relevant configurations can help future developers to understand them. 

Rules Engine with Nected

Implementing a rules engine can be very easy with Nected. Nected allows you to use microservices architecture by providing facilities to use REST API and connect your DB.

Here is how you can implement a simple rules engine with Nected.

Step 1: Connect & Integrate your Database

Connect your database. Next, create datasets using SQL query engine. And, finally, attach data directly with rules.

Step 2: Create & Publish Rule setting dynamic output

Create and publish desired rules with outputs using the no-code editor. Define the conditions, and you can choose desired output formats from constants, JSON, or custom JS formulas.

Step 3: Attach Actions with Rule Results

Define actions and integrate via DB & REST API connectors.

Step 4: Call the rule via API

Integrate your rule into your existing systems or applications using the orchestrations and API features (as you can see below)

Communication Protocols for Microservices Rules Engine

The communication in this architecture is conducted by two primary concepts. They are RESTful APIs and Message Queues.


  • The architecture mainly focuses on RESTful APIs as the protocol for communication between microservices and the rule engine. 
  • RESTful APIs are known for their simplicity and scalability. They always support microservices to exchange data with the rule engine. 
  • HTTP methods is a stateful communication model with well-defined endpoints. RESTful APIs simplify integration to make it comfortable for microservices to submit data for processing the data and fetching the results. 

Message Queues:

  • Message Queues act as an asynchronous mechanism in the architecture. 
  • Microservices can communicate with the rule engine in a decoupled manner by using message queues. 
  • Since microservices do not depend on the availability of the rule engine, the decoupling concept enhances the system’s fault tolerance. 

Microservices Rule Engine Design Pattern

There are two types of microservices rules engine design patterns: 

1. Command Query Responsibility Segregation (CQRS)

2. Event Sourcing Pattern. 

The implementation of the Command Query Responsibility Segregation (CQRS) design pattern in the architecture involves the separation of responsibilities between command and query operations, optimizing performance and scalability. Whereas, the Event Sourcing pattern is responsible for recording and storing the events series.

CQRS Design Pattern: 

  • Command Responsibility: When it comes to executing rules, commands are in charge of starting things like business rules inside the Rule Engine.
  • Query Responsibility: Microservices can get data from the system, possibly even the outcomes of rule executions, thanks to queries, which manage data retrieval activities.

Event Sourcing Pattern: 

  • Record and Store Events: This technique is used to record and store the series of events that lead to the execution of rules. Events are significant occurrences or state shifts.
  • Support for Data Consistency: Data is supported by event sourcing.

Rule Engine Microservice Example

Now, let us see an example scenario where microservices architecture takes action to simplify the process.

Nеctеd's Java orchestration engine allows you to easily manage Java-based microservices. With Nected your company can achieve auto-scaling of Java services, reduce infrastructurе costs by 25%, and improve application performance. Nected’s container orchestration engine plays an important role in simplifying container management. 

To demonstrate rules engine microservice architecture with Nected’s orchestration engine, let’s explore a scenario from the healthcare domain.

Let us consider that we have a sequence of standardized SpringBoot Microservices based on the Fast Healthcare Interoperability Resources (FHIR) Standard Trial Use (STU) data structure. This architecture provides input from the patient, personal history, clinical observations and surveys to gather information about a patient’s health condition. 

Here, the microservices architecture is used to implement business rules to conduct risk assessments for heart disorders, attacks and diabetes by considering the patient’s medical information.

The above architecture depicts the microservices architecture for the hospital scenario discussed earlier. 

Below are the components which can take place in the architecture: 

  • 2SpringBoot - FHIR
  • Red Hat JBoss  - Business Rules Management System (BRMS) 
  • Docker - Packages
  • OpenShift - PaaS for Orchestrating deployments of Microservices
  • Jenkins - For CI/CD pipelines
  • Microservices Github repository

Integrating SpringBoot with Nected

You can integrate Nected with a Spring Boot application by calling the Nected API within the Java-based Spring Boot framework. The integration process is then made by making HTTP requests to this API and handling the responses within your Spring Boot application.

Choosing the Right Rules Engine for Microservices

Choosing the right rules engine is an important step that you must take in your organization. It is very necessary to use an intuitive rules engine like Nected for your software systems. Nected is a fully flexible and customizable Business Rule Management System (BRMS).

Below are a few technical aspects of the Nected rules engine. 

  • Multiple output format: Outputs are in formats such as constants, JSON, or custom JavaScript formulae. 
  • Custom JS code: Manipulate data, transform it, or serve specific purposes with a custom JS code feature. 
  • Simple & Versatile Rule types:  Use Rule Sets, Rule chains and Decision tables
  • Data Connectivity: Attach actions to rules, use DB connectors, and trigger rules easily.


Using the features of rule engine microservices has become popular in all organizations for improving an application’s responsiveness and agile development. This concept is a specialized part made to manage business rules in a microservices architecture. The decision-making logic is contained in business rules to enable systems to adapt different specifications. 

This concept is unavoidable and it has gradually become a mandatory thing in all organizations. Automation in finance, processes in healthcare, and personalization of user experiences in e-commerce, are all improved by the rules engine.


Q1. What is the purpose of a Rule Engine Microservice?

A Rule Engine Microservice is designed to centralize and manage business rules within a microservices architecture. It allows dynamic rule changes without altering the core application, enhancing flexibility and agility in decision-making processes.

Q2.How does a Rule Engine Microservice differ from traditional rule-based systems?

Unlike traditional rule-based systems, a Rule Engine Microservice operates independently and offers scalability and easier maintenance. It enables real-time rule updates and ensures efficient adaptation to changing business requirements without disrupting the entire application.

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