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Also Read: 2021 Top MuleSoft Anypoint Studio interview questions
General MuleSoft, Mule 4 Developer Interview Questions in 2021:
These are the general questions that are asked by an interviewer to get an overview of the technical experience you have with Mule ESB. All these answers are different for different people and purely based on your project experience.
What are the key differences between Mule 3 & Mule 4?
What are the interfaces developed by you? Explain the flow
A. Explain the interfaces (how mule is involved in the integration & transformation) and APIs flow of your project. Also, explain the various connectors you have used for the implementation.
Which version of Mule you have used
A. Based on your experience you can tell either Mule 3.9 or Mule 4.
What are the frontend & backend applications?
A. Explain the frontend application which sends the payload to Mule and the backend application to which the payload is sent.
What HTTP methods you have used
A. GET/POST calls (mention based on your project experience)
Difference between REST & SOAP services
A. REST API has no official standard at all because it is an architectural style. SOAP API, on the other hand, has an official standard because it is a protocol.
REST APIs use multiple standards like HTTP, JSON, URL, and XML while SOAP APIs are largely based on HTTP and XML.
As REST API deploys multiple standards, so it takes fewer resources and bandwidth as compared to SOAP which uses XML for the creation of Payload and results in a large-sized file.
The ways both APIs exposes business logic are also different. REST API takes advantage of URL exposure like @path("/WeatherService") while SOAP API use of services interfaces like @WebService.
SOAP API defines too many standards, and its implementer implements the things in a standard way only. In the case of miscommunication from service, the result will be the error. REST API, on the other hand, doesn't make emphasize on too many standards and results in corrupt API in the end.
REST API uses Web Application Description Language, and SOAP API used Web Services Description language for describing the functionalities being offered by web services.
REST APIs are more convenient with JavaScript and can be implemented easily as well. SOAP APIs are also convenient with JavaScript but don't support for greater implementation.
What are the advantages of Mulesoft
What is a SOAP web service
What is Mule ESB?
Mule ESB is a Java-based enterprise service bus (ESB) and integration platform, a developer can connect their application with ESB. Mule uses service-oriented architecture. Apart from the different technologies the applications use, including JMS, Web Services, SMTP, HTTP. The advantage of ESB, it allows communication in different applications. Messages can be in any format SOAP to JSON. Mule ESB Development provides a messaging framework that enables the exchange of data among applications.
What is the definition of Web Services?
Web service is a function or program in any language that can be accessed over HTTP. Message format can be XML or JSON or any other program as long as the other programs can understand and communicate. Any web service has a server-client relationship. Web services can be synchronous or asynchronous. Any web service can have multiple clients.
Difference between URI & query parameters
A. URI parameter is basically used to identify a specific resource or resources whereas a query parameter is used to sort/filter those resources
How to fetch URI & query parameters in Mule 4?
A. Attributes in Mule 4 replace inbound properties
What is the difference between ESB and JMS?
ESB provides the middleware and interfaces that allow businesses to connect their applications without writing code.
JMS provides the messaging capability and facilitates communication between the modules/applications.
What are the core principles of ESB Integration?
Transportation — Transport protocol negotiation between different formats including JMS, JDBC, HTTP, etc.
Transformation — Transformation of data between certain data formats as needed by every ESB connector individually
Non-functional consistency — The way monitoring and security policies are applied as well as implemented should be consistent
Mediation — This involves offering many different interfaces to:
- Enable different channels to the same unlying component implementation
- Support different service versions for backward compatibility
Explain Flow in Mule ESB.
A flow is a construct within which you link together several individual elements to handle the receipt, processing, and eventual routing of a message.
A Flow is a sequence of message-processing events. A message that enters a flow may pass through a wide variety of processors. In the example diagram below, Mule receives the message through a request-response inbound endpoint, transforms the content into a new format, and processes the business logic in a component before returning a response via the message source.
Explain Batch Jobs in Mule ESB.
A batch job is a top-level element in Mule ESB that exists outside all Mule flows. Batch jobs split large messages into records which Mule processes asynchronously; just as flows process messages, batch jobs process records.
A batch job contains one or more batch steps which, in turn, contain any number of message processors that act upon records.
A batch job executes when triggered by either a batch executor in a Mule flow or a message source in a batch-accepting input. when triggered, Mule creates a new batch job instance. When all records have passed through all batch steps, the batch job instance ends and the batch job result can be summarized in a report to indicate which records succeeded and which failed during processing.
What is the status code for a successful POST call
A. 201
What is Mule Cache Scope and what are its storage types?
Caching in Mule ESB can be done by Mule Cache Scope. Mule Cache Scope has 3 storage types –
In-memory: This stores the data inside system memory. The data stored with In-memory is non-persistent which means in case of API restart or crash, the data been cached will be lost.
Configuration Properties:
- Store Name
- Maximum number of entries
- TTL (Time to live)
- Expiration Interval
Managed-store: This stores the data in a place defined by ListableObjectStore. The data stored with Managed-store is persistent which means in case of API restart or crash, the data been cached will no be lost.
HTTP Status codes
1xx Informational.
2xx Success scenarios
3xx Redirection Errors
4xx Client Errors
5xx Server Errors
Visit for all HTTP status codes
RAML Interview Questions in Mulesoft interviews:
Write a Helloworld RAML?
#%RAML 1.0
title: Hello world # required title
/helloworld: # optional resource
get: # HTTP method declaration
responses: # declare a response
200: # HTTP status code
body: # declare the content of the response
application/json: # media type
type: | # structural definition of response (schema or type)
{
"title": "Hello world Response",
"type": "object",
"properties": {
"message": {
"type": "string"
}
}
}
example: | # example of how a response looks
{
"message": "Hello world"
}
What is RAML?
A. RESTful API Modeling Language (also known as RAML) is a YAML-based modeling language to define RESTful APIs. It provides a structured and rich format to define the API. According to RAML's website, it "makes it easy to manage the whole API lifecycle."
RAML can be used in a multitude of ways: to implement interactive API consoles, create documentation, describing an API you are planning to build, and more. Regardless of the name, RAML can describe APIs that do not follow all of the REST rules
What are the traits and resource type?
A. Traits are like function and are used to define common attributes for HTTP method (GET, PUT, POST, PATCH, DELETE, etc) such as whether or not they are filterable, searchable, or pageable
ResourceType is like a template that is used to specify the descriptions, methods, and parameters that can be used by multiple other resources without the need to rewrite the duplicate code or repeating code.
Can we use two or more methods for a single resource?
A. No, we can use only one HTTP method once for a single resource in RAML. Example: If a resource is “/employees/employee” then we can define GET, PUT POST, PATCH or DELETE HTTP methods only once.
Please go through this article for more MuleSoft Dataweave Interview questions
Anypoint Studio Interview Questions:
What connectors have you used?
A. Salesforce, Sharepoint, JMS, HTTP, File, etc
Difference between VM queue & JMS
A. VM Transport is for intra JVM communication between Mule flows. We can use VM transport to communicate with different flows of the same application whereas JMS is used for communicating with the external applications also.
How to filter duplicate records?
A. Using Idempotent filter to discard duplicate records
What are the core components of Mule ESB?
A. Scheduler, For Each, Logger, Batch (Batch Aggregator, Batch Job, Batch Step), Flow reference, Transform message, Error handling Routers, Scopes and Transformers. Refer Core components of Mule
How to read a file as input other than FTP connector
Scenario: How to fetch and process 5M records(few duplicates) into DB
Different types of flows, flow processing strategies
A. Flow processing strategies in Mulesoft are:
- Synchronous Flow Processing Strategy
- Queued Flow Processing Strategy
- Asynchronous Flow Processing Strategy
- Thread Per Processing Strategy
- Queued Asynchronous Flow Processing Strategy
- Non-blocking Flow Processing Strategy
- Custom Processing Strategy
Difference between sub-flow, private flow
A. Subflow processes messages synchronously but inherits processing strategy and exception handling strategy from the calling flow (parent flow). It can be used to split common logic and be reused by other flows.
Private flow does not use a source. It can be synchronous or asynchronous based on the processing strategy selected. Also, has its own exception handling strategy. Allows you to define different threading profile.
How can we create a custom policy in Anypoint Studio?
A. Navigate to File > New > API custom policy Project(Beta) in Anypoint Studio
Difference between async flow & async scope
Async Flow: Async Flow is a transactional flow in which the requestor does not wait for the response from the target service and processes the flow
Async scope: The Async scope is a branch processing block that executes simultaneously with the main flow. The main flow continues to execute while it initiates and processes the Async scope
Error handling in Mule 3.9
A. Refer here for the Error handling mechanism in Mule 3.9
How do you consume a SOAP-based web service in Studio
A. Using the Web Service Consumer component. Configure the connector with WSDL or SOAP web service configuration details like Service name, URL, Binding port, etc.
Steps involved in MUnit creation
How do you set environment-specific values in the Mule application?
At first, Create a properties file for each development environment in your application. Configure a properties placeholder in your app to look for the environment upon launch. Set an environment variable to point to a specific development environment during application deployment.
Explain Collection aggregator, splitter, object store, cache
What are the variables available in Mule 3?
A. Flow variables, Record variables, Session variables
How do you import a RAML and use in Anypoint Studio
Mulesoft Anypoint Studio questions and answers
Anypoint Platform Interview Questions:
How do you deploy API
What is the difference between Rate limiting and Throttling
Mulesoft Anypoint Platform Interview questions and answers
Cloudhub Interview Questions:
Implementation of API & Deploying to Cloudhub
Mule Runtime manager interview questions answers
APIs Interview Questions:
What are the different types of APIs in API led architecture
Dataweave Interview Questions:
Use of pluck
Use of map, map object, reduce
Difference between DW1.0 & DW2.0
Use of lookup, p, causedBy functions
Mulesoft Dataweave Interview questions and answers
Mule 4 Interview Questions:
Advancements in Mule 4
Error handling mechanism
What are the variables available in Mule 4
What is Anypoint Exchange in MuleSoft?
Anypoint Exchange provides the benefit of being able to discover, share, and incorporate assets and resources into your applications. Anypoint Exchange helps you create API developer portals, view and test APIs, simulate data to APIs (Mocking Service), create assets, and use API Notebooks to describe and test API functions.
Find the latest MuleSoft(Mule 4) Articles on DataWeave, Anypoint Studio, Anypoint Platform, and Runtime Manager. Our articles also include frequently asked Mule4 Interview questions and answers. Please comment below for any queries or free article submissions.
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