MuleSoft Interview Questions for beginners and experienced

1. What is Mulesoft? Answer: MuleSoft provides the most widely used integration platform (Mule ESB &CloudHub) for connecting SaaS& enterprise applications in the cloud and on-premise. (mulesoft interview questions top 50)

2. What is a REST web service? Answer: Representational State Transfer (REST) is an architectural style that specifies constraints, such as the uniform interface, that if applied to a web service induce desirable properties, such as performance, scalability, and modifiability, that enable services to work best on the Web.

3. What is Flow Processing Strategies? Answer:
  • 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, Rollback Exception Handling.
4. What is caching and why to use it? Answer: Caching is a concept that is used to store frequently used data in the memory, file system or database which saves processing time and load if it would have to be accessed from source location every time.

5. How can we create and consume SOAP service in Mule? Answer: Creating SOAP Service – We can create a SOAP service same as we create Mule Project With RAML, the only change is instead of RAML we need to import Concert WSDL. Consuming SOAP Service – We can use Web Service Consumer or CXF component in our mule flow to access/consume SOAP service. (Online Training Institute)

6. What are Shared Resources in Mule and how are they been used? Answer: We can make connectors as a reusable component by defining them as common resources and expose them to all applications deployed under the same domain, these resources are known as shared resources. These shared resource needs to be defined inside Mule Domain Project and then referred to each of the projects that are meant to use the elements in it.
7. What are the different types of flow? Answer: Subflow – A subflow is always synchronous. It is similar to asynchronous flow, subflow executes in the same thread of the calling process. The calling process triggers the sub-flow and waits for it to complete and resumes once the sub-flow hascompleted. Synchronous Flow– Same as sub-flow, the only difference is that in synchronous flows you need to separately define an exception strategy to it, it does not inherit the exception strategy of its calling flow. Asynchronous Flow – As in sub-flow and synchronous flow, calling process triggers the sub-flow and waits for it to complete; for asynchronous flow the flow.  The calling process triggers an asynchronous flow and moves ahead to its next activity. An asynchronous flow executes in parallel to its calling/parent flow in a different thread. An asynchronous flow does not return its output to its parent/calling flow. Private Flow – a flow that does not have an inbound connector in the source. This means a private flow cannot start on its own on receiving the inbound message as it does not have an inbound connector, A private flow can only be called using flow-ref same as sub-flow.
8. What is Shared Resource in Mule and how they have been used? Answer: We can make connectors as a reusable component by defining them as common resources and expose them to all applications deployed under the same domain, these resources are known as shared resources. These shared resource needs to be defined inside Mule Domain Project and then referred to each of the projects that are meant to use the elements in it.
9. Why Mule Was Designed? Answer: Mule’s core was designed as an event-driven framework combined with a unified representation of messages, expandable with pluggable modules. These module would provide support for a wide range of transports or add extra features, such as distributed transactions, security, or management. The mule was also designed as a programmatic framework offering programmers the means to graft additional behavior such as specific message processing or custom data transformation.
10. How can you change the runtime changes using mediation primitive? Answer: We have a future called Promotable properties in ESB. We can configure this future while development. Then we can make it changed at runtime without restarting the server it can be published.
11. What Is a Router In Mule? Answer: Routers play a crucial role in controlling the trajectory a message will follow when it transits in Mule. They are the gatekeepers of the endpoints of service, taking care of keeping messages on the right succession of tracks so they can reach their intended destinations. Certain routers act like the big classification yards: they can split, sort, or regroup messages based on certain conditions.
12. What are the different types of Primitives used in Mediation? Answer: These are the different types of primitives in mediation: 1. Message Filter 2. Type Filter 3. Endpoint Lookup 4. Service Invoke 5. Fan-out 6. Fan-in 7. XSLT 8. BO Map 9. Message Element Setter 10. DB lookup 11. Data Handler 12. Custom Mediation 13. Header Setters 14. Message Logger 15. Even Emitter 16. Stop 17. Fail 18. Sub Flow
13. How Mule ESB works? Answer: Mule is based on the concept of Event-Driven Architecture (EDA), works by responding to messages initiated by external resources (that is, events). Mule applications accept and process events as messages through several message processors plugged together in a flow. Alternatively, large or streaming messages can be processed as records in a batch job. Every Mule flow contains a series of message processors that accept, then process messages. Mule applications usually contain multiple linked flows and/or batch jobs, which, in combination, perform the integration required for your use case.
14. What are the main features of Mule ESB? What are the different ESBs in the market? Answer: 1)The main features of Mule ESB are: • It is very simple and easy to use-Drag and drops Graphical design • SLA monitoring and API management • High scalability • We can deploy in a One-click cloud or on-premise deployments 2)Different ESB’s in Market are:
  • Talend
  • Mule ESB
  • JBoss Fuse ESB
15. What Is Global Endpoint In Mule? Answer: An endpoint destination that is shared by several routers, it is worth creating a global endpoint. A global endpoint is not typified for inbound or outbound routing, making it usable in many different places in a configuration file. It must be named so it can be used in a service, which will reference the global endpoint by its name. A global endpoint can also help clarify the usage of a particular destination.
16. What Is Model Layer In Mule? Answer: The first logical layer is the model layer. A Mule model represents the runtime environment that hosts services. It defines the behavior of Mule when processing requests handled by services. The model provides services with supporting features, such as exception strategies. It also provides services with default values that simplify their configuration.
17. What Is Bridge Component In Mule? Answer: A bridge component is used to pass the messages from the inbound router to the outbound one.(Mulesoft Training ) A bridge is a neutral component: it does not perform any action or modify messages that it processes. A bridge component is used to pass the messages from the inbound router to the outbound one. A bridge is a neutral component: it does not perform any action or modify messages that it processes.
18. What are the advantages of using an ESB? Answer: Provides a way for endpoints to connect without having to directly talk to each other. It simplifies the communications for the endpoints as they only have to conform to a standard communication interface, the bus. An ESB provides a single place to get some key endpoint metrics: frequency, availability, and performance. An ESB tends to provide more than one communication interface. However, a developer-only needs to choose the easiest one to get and receive the data from the bus.
19. Why Mule is preferred than other ESB implementations? Answer: Mule is lightweight but highly scalable, allowing you to start small and connect more applications over time. The ESB manages all the interactions between applications and components transparently, regardless of whether they exist in the same virtual machine or over the Internet, and regardless of the underlying transport protocol used. Several commercial ESB implementation provides limited functionality or built on top of an existing application server or messaging server, locking you into that specific vendor. Mule is vendor-neutral, so different vendor implementations can plug into it. You are never locked in to a specific vendor when you use Mule.
20. Explain Batch Jobs in Mule ESB? Answer: 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.
21. What are various types of Exception Handling? Answer: 1. Choice Exception Handling. 2. Catch Exception Handling. 3. Rollback Exception Handling. 4. Global Exception Handling. 5. Default Exception Handling.
22. What is the functionality of Fan-in and Fan-out? Answer: Fan-out: We can use the Fan Out primitive to fire the output terminal once (with the input message) or fire the output terminal multiple times. You can use Fan Out in isolation or as part of a Fan-Out and Fan In combination. Fan-In: Fan In is always partnered with a Fan-Out in the same flow and acts as a decision point for when to continue flow execution. It receives several messages until a decision point is reached, at which point the last message to be received is propagated to the output terminal. The Fan In primitive may only be used in combination with Fan-Out.
23. What Are Configuration Builders In Mule? Answer: Mule uses configuration builders that can translate a human-authored configuration file into the complex graph of objects that constitutes a running node of this ESB. The main builders are of two kinds: a Spring-driven builder, which works with XML files, and a script builder, which can accept scripting language files.
24. Explain Mule Expression Language (MEL)? Answer: MEL is a lightweight, Mule-specific expression language that you can use to access and evaluate the data in the payload, properties, and variables of a Mule message. Accessible and usable from within virtually every message processor in Mule, MEL enables you to quickly and elegantly filter, route, or otherwise act upon the different parts of the Mule message object.
25. What are Batch Jobs in Mule ESB? Answer: A batch job is a top-level element in Mule which exists outside all Mule flows. Batch jobs split large messages into records which Mule processes asynchronously in a batch job; 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 as they move through the batch job. During batch processing, you can use record-level variables (recorders) and MEL expressions to enrich, route or otherwise act upon records.
26. Explain Flow in Mule ESB? Answer: A flow is a construct within which you link together several individual elements to handle the receipt, processing, and eventual routing of a message. 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.
27. What is Transient Context? Answer: Transient Context: Used for passing values between Mediation primitives within the current flow — either the request flow or the responses flow. The transient context cannot link requests and responses and hence cannot be used across. Used when you want to save an input message before a service invokes call (within a request or response flow). After the services invoke call, the next primitive can create another message by combining the service invoke a response and the original message stored in the transient context.
28. Do you have any particular areas of interest or ability? Answer: Talk to the interviewer about your strengths and be sure to highlight any particular skill that you excel in. It’s a great idea, if you can, to highlight specific skills that may be listed on the company’s job posting/job description. If there is a related area of interest where you’d like to expand your skills, you can mention those as well.
29. What is the MuleSoft Anypoint platform used for? Answer: MuleSoft’s Anypoint Platform of integration products is designed to tie together software as a service (SaaS) and on-premises software.
30. What are the advantages of Soap Web Services? Answer: WS Security: SOAP defines its security known as WS Security. Language and Platform independent: SOAP web services can be written in any programming language and executed in any platform. Disadvantages of Soap Web Services: Slow: SOAP uses XML format that must be parsed to be read. It defines many standards that must be followed while developing SOAP applications. So it is slow and consumes more bandwidth and resources. WSDL dependent: SOAP uses WSDL and doesn’t have any other mechanism to discover the service.
31. What are the different types of Flow Processing Strategies Answer: There are six different types of Flow Processing Strategies. They are 1. Asynchronous Flow Processing Strategy. 2. Custom Processing Strategy. 3. Thread Per Processing Strategy. 4. Queued Asynchronous Flow Processing Strategy. 5. Synchronous Flow Processing Strategy. 6. Non-blocking Flow Processing Strategy. 7. Queued Flow Processing Strategy.
32. What is ESB? Answer: An enterprise service bus (ESB) is software architecture for middleware that provides fundamental services for more complex architectures. For example, an ESB incorporates the features required to implement a service-oriented architecture (SOA). In a general sense, an ESB can be thought of as a mechanism that manages access to applications and services (especially legacy versions) to present a single, simple, and consistent interface to end-users via Web- or forms-based client-side front ends.
33. When do we need ESB? Answer: Mule and other ESBs offer real value in scenarios where there are at least a few integration points or at least 3 applications to integrate. They are also well suited to scenarios where loose coupling, scalability, and robustness are required.
34. How did you find MuleSoft? Answer: I found MuleSoft a little bit by coincidence. My wife got a job at UCSF so we moved here from Stockholm and while waiting for the paperwork to process I found out that MuleSoft’s HQ was located in San Francisco. Since I had tested Mule ESB at my previous job to build integrations and had liked the product, I thought I would apply.
35. How Message In Mule Is Composed? Answer: A Mule message is composed of different parts: The payload, which is the main data content carried by the message. The properties, which contain the meta information much like the header of a SOAP envelope or the properties of a JMS message. Optionally, multiple named attachments, to support the notion of multipart messages. 36. What Is Transport Layer In Mule? Answer: The transport layer is in charge of receiving or sending messages. This is why it is involved with both inbound and outbound communications. A transport manifests itself in the configuration by the following elements: connectors, endpoints, and transformers.
A transport also defines one message adapter. A message adapter is responsible for extracting all the information available in a particular request (data, meta information, attachments, and so on) and storing them in transport-agnostic fashion in a Mule message.
37. Explain ESB Integration core principles? Answer: Transformation: Data transformation between canonical data formats and specifi data formats required by each ESB connector. Transportation: Transport protocol negotiation between multiple formats. Such as HTTP, JMS, JDBC. Mediation: Providing multiple interfaces for a) supporting multiple versions of a service for backward compatibility or b) to allow for multiple channels to the same underlying component implementation. This second the requirement may involve providing multiple interfaces to the same component, one legacy interface (flat file) and one standards-compliant (SOAP/XML) interface. Non-functional consistency: For a typical ESB initiative, this can include consistency around the way security and monitoring policies are applied and implemented.
38. What Are Differences Between Mule And Other Commercial Tabs? Answer: Prescriptive deployment model, whereas Mule supports a wide variety of deployment strategies. Prescriptive SOA methodology, whereas Mule can embrace the architectural style and SOA practices in place where it is deployed. Mainly focused on higher-level concerns, whereas Mule deals extensively with all the details of integration. Strict full-stack web service orientation, whereas Mule’s capacities as an integration framework open it to all sorts of other protocols. Comprehensive documentation, a subject on which Mule Source has made huge progress recently.
39. Why Mule Was Designed? Answer: Mule’s core was designed as an event-driven framework combined with a unified representation of messages, expandable with pluggable modules. These modules would provide support for a wide range of transports or add extra features, such as distributed transactions, security, or management. The mule was also designed as a programmatic framework offering programmers the means to graft additional behavior such as specific message processing or custom data transformation.
40. What Is Endpoint In Mule? Answer: An endpoint represents the specific usage of a protocol, whether it is for listening/polling, reading from, or writing to a particular target destination. Hence it controls what underlying entities will be used with the connector they depend on.The target destination itself is defined as a URI. Depending on the connector, the URI will bear a different meaning; for example, it can represent a URL or a JMS destination.
41. What Is Connector In Mule? Answer: A connector is in charge of controlling the usage of a particular protocol. It is configured with parameters that are specific to this protocol and holds any state that can be shared with the underlying entities in charge of the actual communications. For example, a JMS connector is configured with a Connection, which is shared by the different entities in charge of the actual communication.
42. What Difficulties Mule Does Encompass? Answer: Transport: applications can accept input from a variety of means, from the file system to the network. Data format: speaking the right protocol is only part of the solution, as applications can use almost any form of representation for the data they exchange. Invocation styles: synchronous, asynchronous, or batch call semantics entail very different integration strategies. Life cycles: applications of different origins that serve varied purposes tend to have disparate development, maintenance, and operational life cycles.
43. When Does Mule Instantiate A Connector? Answer:  If Mule figures out that one of our endpoints needs a particular connector, it will automatically instantiate one for us, using all the default values for its different configuration parameters. This is a perfectly viable approach if we are satisfied with the behavior of the connector when it uses its default configuration. This is often the case for the VM or HTTP transports. Note that Mule will name these default connectors with monikers such as a connector.
44. What Is Component In Mule? Answer: Components are the centerpiece of Mule’s services. Each service is organized with a component at its core and inbound and outbound routers around it. Components are used to implement a specific behavior in service. This behavior can be as simple as logging messages or can go as far as invoking other services. Components can also have no behavior at all; in that case, they are pass-through and make the service act as a bridge between its inbound and outbound routers.
45. What Is Transport Service Descriptor In Mule? Answer: The connector has a technical configuration known as the Transport Service Descriptor (TSD). This hidden configuration is automatically used for each instance of the connector. It defines technical parameters such as what classes to use for the message receivers, requesters, and dispatchers; or the default transformers to use in inbound, outbound, and response routers. Knowing these default values is essential to grasping the behavior of transport.
46. A most embarrassing moment? Answer: I once got locked out of a sauna in the middle of winter (in Sweden), without any clothes. My friend managed to get a hold of a briefcase-sized mobile phone (this was a while ago) and called for someone with an additional key to let us in again.
47. Why we use RAML? Answer: RAML helps the client know, what the service is and how all the operations can be invoked. RAML helps the developer in creating the initial structure of this API. RAML can also be used for documentation purposes.
48. Why do we need ESB? Answer: ESB, a middleware technology, is a Bus-like architecture used to integrate heterogeneous systems. In ESB, each application is independent and yet able to communicate with other systems. It, thus, prevents scalability issues and ensure that communication happens only through it.
49. What is Mulesoft used for? Answer: Mulesoft is an integration platform that allows developers to connect applications quickly and easily, enabling them to exchange data.

50. What is Shared Context? Answer: Shared Context: Context is a temporary area that is created along with Service Message Object (SMO) in the Mediation Flows. Shared Context is a type of context which is present in the SMO. Shared Context is mainly used when we are using the Aggregation process where we need to Iterate the BO for Certain times. Shared Context maintains Aggregation data between Aggregation (FanOut and FanIn) primitives. The Content (data) which is present in the shared context BO does not persist across Request and Response flows i.e The Data in the Shared Context which is used in Request flow can not be used again in Response flow.

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