#GIT

Last updated    - V6 (17-Sep-2025)

Key Concepts

Topic	SubTopic	Basic	Intermediate	Advanced	Expert
Introduction	What is Git, Version Control concepts, Git vs SVN	✅	✅	✅	✅
Installation & Setup	Install Git, Initial configuration, SSH keys	✅	✅	✅	✅
Core Concepts	Repository, Working directory, Staging area	✅	✅	✅	✅
Basic Commands	git init, git clone, git add, git commit, git status, git log	✅	✅	✅	✅
Branching	git branch, git checkout, git switch, git merge	✅	✅	✅	✅
Remote Repositories	git remote, git fetch, git pull, git push	✅	✅	✅	✅
Collaboration	Forking, Pull requests, Code review workflow		✅	✅	✅
Merging & Conflicts	Merge strategies, Conflict resolution, Rebase basics		✅	✅	✅
Stashing & Cleaning	git stash, git clean, temporary changes		✅	✅	✅
Advanced Branching	git rebase, cherry-pick, revert, reset			✅	✅
Tags & Releases	Annotated tags, Lightweight tags, Versioning	✅	✅	✅	✅
Undo & Recovery	git reflog, reset, revert, checkout recovery		✅	✅	✅
Git Internals	Object model, Blobs, Trees, Commits, SHA-1			✅	✅
Hooks & Customization	Git hooks, Aliases, Custom configs			✅	✅
Performance & Scaling	Large repos, Git LFS, Submodules, Monorepos			✅	✅
Security	GPG commit signing, Credential management		✅	✅	✅
CI/CD Integration	GitHub Actions, GitLab CI, Jenkins with Git		✅	✅	✅
Best Practices	Commit message guidelines, Branch strategy (GitFlow, trunk-based), Code reviews	✅	✅	✅	✅
Tools & GUIs	GitHub Desktop, SourceTree, GitKraken, IDE plugins	✅	✅	✅	✅
Troubleshooting	Common errors, Detached HEAD, Merge issues, Debugging history		✅	✅	✅

Interview question

1. Git Basics

1. What is Git, and why is it used?
2. What is the difference between Git and other VCS like SVN?
3. Explain the difference between a repository, a working directory, and a staging area.
4. How do you initialize a new Git repository?
5. How do you clone a repository?
6. What does git add do?
7. What does git commit do?
8. What is the difference between git commit -m and git commit -a?
9. What is the difference between git status and git log?
10. Explain the difference between git fetch and git pull.
11. What does git push do?
12. How do you check the current Git configuration?
13. How do you create a .gitignore file?
14. How do you check the version of Git installed?
15. What is the difference between a bare repository and a non-bare repository?
16. How do you rename a Git branch locally?
17. What does HEAD mean in Git?
18. How do you delete a branch in Git locally?
19. How do you delete a branch in Git remotely?
20. How do you configure a global username and email in Git?

---

2. Branching & Merging

1. What is a branch in Git?
2. How do you create a branch in Git?
3. How do you switch between branches?
4. What is the difference between git checkout and git switch?
5. How do you list all branches in Git?
6. How do you rename a branch?
7. How do you merge one branch into another?
8. What is a fast-forward merge?
9. What is a three-way merge?
10. What are merge conflicts in Git?
11. How do you resolve merge conflicts?
12. What is the difference between merge and rebase?
13. What does git cherry-pick do?
14. How do you undo a merge?
15. What is the difference between git reset and git revert?
16. How do you create a tracking branch?
17. What is the purpose of git branch -vv?
18. What is a detached HEAD state?
19. How do you move a commit from one branch to another?
20. Explain GitFlow branching strategy.

---

3. Remote Repositories

1. What is a remote in Git?
2. How do you add a remote repository?
3. How do you list all remotes in Git?
4. How do you remove a remote repository?
5. How do you rename a remote repository?
6. What does origin mean in Git?
7. How do you fetch changes from a remote without merging?
8. What is the difference between git fetch and git pull?
9. How do you push changes to a remote branch?
10. How do you push a new local branch to a remote repository?
11. How do you set a default remote branch for pushing?
12. How do you track a remote branch locally?
13. What is the purpose of git remote -v?
14. How do you force push changes in Git?
15. What are the risks of git push --force?
16. How do you safely force push without overwriting others? changes?
17. How do you delete a branch in a remote repository?
18. How do you check if a branch exists in a remote repo?
19. What is a fork in Git, and how is it different from a clone?
20. How do you sync a fork with the upstream repository?

---

4. Staging, Stash & Clean

1. What is the staging area in Git?
2. How do you add files to the staging area?
3. How do you remove files from the staging area?
4. What does git diff do?
5. What does git diff --staged show?
6. How do you unstage a file?
7. What is Git stash?
8. How do you stash changes?
9. How do you apply stashed changes?
10. How do you list all stashes?
11. How do you drop a stash?
12. How do you clear all stashes?
13. How do you apply a stash without removing it?
14. How do you stash untracked files?
15. What is the difference between git stash pop and git stash apply?
16. What does git clean do?
17. How do you remove untracked files in Git?
18. How do you remove ignored files in Git?
19. What is the difference between tracked and untracked files?
20. How do you check which files are ignored in Git?

---

5. Undo & Recovery

1. How do you undo the last commit?
2. What does git reset do?
3. Difference between git reset --soft, --mixed, and --hard.
4. How do you revert a commit?
5. What does git reflog do?
6. How do you recover a deleted branch?
7. How do you find a lost commit in Git?
8. What is an orphan branch?
9. How do you go back to a previous commit?
10. What is the difference between git reset HEAD^ and git reset --hard HEAD^?
11. How do you undo changes to a file before staging?
12. How do you undo changes to a file after staging?
13. How do you remove the last commit without deleting changes?
14. How do you squash commits?
15. How do you amend the last commit message?
16. How do you move commits to another branch?
17. How do you recover a commit after rebase?
18. What is the difference between git checkout and git restore?
19. How do you discard all local changes in Git?
20. What is the difference between git reset and git checkout?

---

6. Git Internals

1. Explain the Git object model.
2. What are blobs, trees, and commits in Git?
3. What is the purpose of SHA-1 in Git?
4. Where does Git store its data?
5. What is .git directory?
6. What are Git references?
7. What is HEAD in Git?
8. What is a Git object hash?
9. How does Git ensure data integrity?
10. Explain the concept of Git snapshots vs diffs.
11. What is the difference between Git index and working tree?
12. What is a packed object in Git?
13. What is git gc?
14. What is the purpose of git fsck?
15. How does Git compress objects?
16. Explain Git pack files.
17. What is git cat-file used for?
18. What is git hash-object?
19. How does Git handle large files?
20. Explain Git internals vs Git commands.

---

7. Collaboration & Workflow

1. What is a pull request?
2. What is the difference between a pull request and a merge request?
3. How do you create a pull request in GitHub?
4. What is the purpose of code reviews in Git workflows?
5. What is GitHub flow?
6. What is GitLab flow?
7. What is trunk-based development?
8. Explain feature branching workflow.
9. Explain release branching workflow.
10. What is the GitFlow workflow?
11. What is the difference between GitHub flow and GitFlow?
12. What is a hotfix branch?
13. What is a long-lived branch?
14. What is the difference between main and master branch?
15. How do you enforce branch protection rules?
16. How do you enforce commit message guidelines?
17. How do you squash commits in a pull request?
18. How do you rebase a pull request?
19. How do you resolve conflicts in a pull request?
20. How do you maintain a clean Git history?

---

8. Advanced Commands & Techniques

1. What does git bisect do?
2. How do you use git bisect to find a bug?
3. What does git blame do?
4. How do you use git blame effectively?
5. What does git shortlog do?
6. What does git describe do?
7. What does git rev-parse do?
8. What does git show do?
9. What does git archive do?
10. What is git bundle?
11. How do you split a commit into multiple commits?
12. How do you combine multiple commits into one?
13. How do you sign a commit with GPG?
14. What does git verify-commit do?
15. What does git verify-tag do?
16. What does git notes do?
17. What is the difference between git submodule and git subtree?
18. How do you add a Git submodule?
19. How do you update a Git submodule?
20. How do you remove a Git submodule?

---

9. CI/CD Integration

1. How do you integrate Git with Jenkins?
2. What is GitHub Actions?
3. How do you trigger a pipeline from a Git commit?
4. What is the difference between webhooks and polling?
5. How do you use Git in a Jenkins pipeline?
6. How do you automate tests with GitHub Actions?
7. How do you deploy code using GitLab CI?
8. What is the difference between GitHub Actions and GitLab CI?
9. How do you use Git tags in CI/CD pipelines?
10. What is the role of Git in DevOps?
11. How do you enforce code quality checks in Git workflows?
12. How do you rollback a deployment using Git?
13. How do you use Git in Kubernetes deployments?
14. What is GitOps?
15. How do you implement GitOps?
16. What tools are used for GitOps?
17. How do you automate semantic versioning with Git?
18. How do you use Git for continuous delivery?
19. What are GitHub Packages?
20. What is the difference between GitHub Packages and Artifactory?

---

10. Security & Best Practices

1. How do you sign commits in Git?
2. What is the importance of signed commits?
3. How do you verify a signed commit?
4. How do you securely store Git credentials?
5. What is the use of Git credential helper?
6. How do you rotate Git credentials?
7. What is the difference between HTTPS and SSH for Git?
8. How do you enforce branch policies in GitHub?
9. What is the principle of least privilege in Git access control?
10. How do you prevent accidental force pushes?
11. How do you prevent committing secrets to Git?
12. What is Git-secrets tool?
13. What is pre-commit hook?
14. What is the difference between client-side and server-side hooks?
15. How do you use Git hooks for code quality enforcement?
16. How do you enforce commit message conventions?
17. How do you maintain a clean commit history?
18. How do you choose a branching strategy for a project?
19. What are common Git anti-patterns?
20. What are Git best practices for large teams?

Related Topics

#Spring_Framework

Last updated    - V4 (16-Sep-2025)

Key Concepts

Topic	Sub-Topics (comma separated)	Basic	Intermediate	Advanced	Expert
Core Container	Beans, BeanFactory, ApplicationContext, Bean Scopes, Bean Lifecycle, Dependency Injection (DI), Inversion of Control (IoC)	✅	✅	✅	✅
Configuration	XML Configuration, Java-based Configuration, Annotation-based Configuration, Environment Profiles, Externalized Configuration	✅	✅	✅	✅
Spring Context	ApplicationContext, MessageSource, Internationalization (i18n), Event Handling, ApplicationListener	✅	✅	✅	✅
Spring AOP	AOP Concepts, Join Points, Pointcuts, Advice, Aspects, Proxying, AspectJ Integration		✅	✅	✅
Data Access (DAO)	JDBC Template, DataSource, Transaction Management, Exception Translation, ORM Integration		✅	✅	✅
Spring ORM	Hibernate Integration, JPA Support, EntityManager, SessionFactory, Transactional Annotations		✅	✅	✅
Spring Transactions	Programmatic Transactions, Declarative Transactions, Propagation, Isolation Levels, Rollback Rules		✅	✅	✅
Spring MVC	DispatcherServlet, Controllers, HandlerMapping, ViewResolver, ModelAndView, Form Handling, Validation	✅	✅	✅	✅
Spring REST	REST Controllers, @RestController, @RequestBody, @ResponseBody, Content Negotiation, Exception Handling		✅	✅	✅
Spring WebFlux	Reactive Programming, Mono, Flux, Functional Endpoints, Reactive Repositories			✅	✅
Spring Security	Authentication, Authorization, Security Filters, UserDetailsService, Password Encoding, JWT, OAuth2		✅	✅	✅
Spring Boot	Auto-Configuration, Starters, Actuator, Spring Boot CLI, Spring Initializr, Properties & YAML	✅	✅	✅	✅
Spring Data	Spring Data JPA, Spring Data MongoDB, PagingAndSortingRepository, CrudRepository, Custom Queries		✅	✅	✅
Spring Cloud	Config Server, Eureka, Zuul/Gateway, Ribbon, Feign, Hystrix, Sleuth, Cloud Bus			✅	✅
Spring Batch	Job, Step, Tasklet, ItemReader, ItemWriter, JobLauncher, Retry & Skip Logic			✅	✅
Spring Integration	Messaging, Channels, Transformers, Routers, Adapters, Gateways, Enterprise Integration Patterns			✅	✅
Spring Testing	Unit Testing with JUnit, MockMvc, @SpringBootTest, Test Slices, Embedded Database Testing	✅	✅	✅	✅
Spring Messaging	JMS, AMQP, STOMP, WebSockets, MessageConverters, RabbitMQ/Kafka Integration			✅	✅
Spring Reactive	Reactive Streams, Reactive Data Access, Backpressure, Reactor Core, WebFlux Security			✅	✅
Spring GraphQL	Spring for GraphQL, DataFetchers, Schema Mapping, Subscriptions, GraphQL + WebFlux			✅	✅

Interview question

1. Introduction & Basics

1. What is AOP (Aspect-Oriented Programming)?
2. What are the advantages of using AOP?
3. Difference between AOP and OOP.
4. What are typical use cases of AOP?
5. How does AOP help in modularizing cross-cutting concerns?
6. What are cross-cutting concerns?
7. Difference between core Spring and Spring AOP.
8. What is the difference between static and dynamic AOP?
9. What is weaving in AOP?
10. Difference between compile-time and runtime weaving.

---

2. Core Concepts

1. What is an Aspect in Spring AOP?
2. What is a Join point?
3. What is Advice in Spring AOP?
4. What is a Pointcut?
5. What is Introduction in AOP?
6. Difference between Aspect, Advice, and Pointcut.
7. What is a Target object?
8. How is a Proxy related to Spring AOP?
9. What are the types of Join points in Spring?
10. What is AspectJ and its relation to Spring AOP?

---

3. Types of Advice

1. What is Before Advice?
2. What is After Advice?
3. What is AfterReturning Advice?
4. What is AfterThrowing Advice?
5. What is Around Advice?
6. Difference between Before and Around Advice.
7. How to implement custom logic in Around Advice?
8. How to access method arguments in Advice?
9. How to modify return value in AfterReturning Advice?
10. How to handle exceptions in AfterThrowing Advice?

---

4. Pointcut Expressions

1. What is a Pointcut Expression?
2. How to use execution() in pointcut expressions?
3. How to use within() in pointcut expressions?
4. How to use args() in pointcut expressions?
5. How to use @annotation() in pointcut expressions?
6. How to use bean() in pointcut expressions?
7. Difference between execution() and within().
8. How to combine multiple pointcut expressions?
9. How to create reusable pointcut expressions?
10. How to test pointcut expressions?

---

5. Aspect Implementation

1. What is @Aspect annotation used for?
2. How to use @Before annotation?
3. How to use @After annotation?
4. How to use @Around annotation?
5. How to use @AfterReturning annotation?
6. How to use @AfterThrowing annotation?
7. How to inject dependencies into an Aspect?
8. How to order aspects using @Order?
9. Difference between XML-based and annotation-based aspects.
10. How to define multiple advices in a single aspect?

---

6. Weaving

1. What is weaving in AOP?
2. Difference between compile-time, load-time, and runtime weaving.
3. How does Spring implement runtime weaving?
4. How to enable load-time weaving in Spring?
5. What are AspectJ weaver and proxy-based weaving?
6. How to debug issues in weaving?
7. Difference between proxy-based AOP and AspectJ AOP.
8. How does Spring choose JDK Dynamic Proxy vs CGLIB?
9. How to force CGLIB proxy in Spring?
10. How does AOP proxy affect class hierarchy?

---

7. Spring AOP Proxy

1. What is a proxy in Spring AOP?
2. Difference between JDK Dynamic Proxy and CGLIB Proxy.
3. How does Spring decide which proxy to use?
4. How to access the underlying target object?
5. How does proxy affect equals() and hashCode()?
6. How to apply multiple advices on a single proxy?
7. How to test proxy objects?
8. How to handle self-invocation in proxies?
9. Difference between interface-based and class-based proxy.
10. How to use ProxyFactoryBean?

---

8. Order & Precedence

1. How to order multiple aspects using @Order annotation?
2. How does Spring determine execution order of advices?
3. Difference between global and local aspect order.
4. How to set priority for specific advices?
5. How to debug advice execution order?
6. How to apply conditional advice execution?
7. How to combine multiple pointcuts with order?
8. How to prevent circular advice calls?
9. How to test order in unit tests?
10. How to document execution order of aspects?

---

9. Exception Handling

1. How to handle exceptions in AOP advice?
2. How to propagate exceptions from Advice?
3. How to implement retry logic in Around Advice?
4. How to implement fallback methods in Advice?
5. How to log exceptions centrally using AOP?
6. How to combine exception handling and transaction management?
7. How to prevent exception swallowing in advices?
8. How to implement custom exception hierarchies in AOP?
9. How to test exception handling in aspects?
10. How to use @AfterThrowing to notify external systems?

---

10. Integration & Advanced Topics

1. How to integrate Spring AOP with Spring Boot?
2. How to use AOP for logging method execution time?
3. How to implement security using AOP?
4. How to implement caching using AOP?
5. How to profile applications using AOP?
6. How to use AOP with transactions?
7. How to implement custom annotations for aspects?
8. How to test AOP in integration tests?
9. What are best practices for writing aspects?
10. Common pitfalls when using Spring AOP.

---

Related Topics

Spring_Boot

Spring_Framework

Spring_Cloud

Spring_Rest

Spring_AOP

Spring_Batch

Spring_MVC

Spring_Security

Spring_AI

#Solace

Last updated    - V4 (16-Sep-2025)

Topic	Sub-Topics	Basic	Intermediate	Advanced	Expert
Introduction	What is Solace, Messaging patterns, Pub/Sub, Queueing, Use cases	✅	✅
Architecture	Solace Message Broker, Components, Clustering, Redundancy	✅	✅	✅
Messaging Concepts	Topics, Queues, Subscriptions, Durable/Non-durable, Guaranteed vs Direct	✅	✅	✅	✅
Producers	Publishing messages, QoS levels, Message properties, API usage	✅	✅	✅	✅
Consumers	Receiving messages, Subscriptions, Queue handling, Event-driven consumption	✅	✅	✅	✅
APIs & SDKs	Solace Java API, JMS API, REST API, MQTT support	✅	✅	✅	✅
Administration	Broker configuration, VPNs, Users & ACLs, Monitoring	✅	✅	✅	✅
Security	Authentication, Authorization, Encryption, ACLs, TLS/SSL	✅	✅	✅	✅
High Availability	Active/Standby, HA clusters, Disaster recovery		✅	✅	✅
Performance & Tuning	Message throughput, Latency optimization, Resource tuning		✅	✅	✅
Advanced Features	Message replay, Guaranteed delivery, Transactional messaging, Event broker routing		✅	✅	✅
Monitoring & Logging	System monitoring, Metrics, Tracing, Alerting	✅	✅	✅	✅
Integration	Microservices, Spring Boot integration, Cloud deployment	✅	✅	✅	✅
Troubleshooting	Common issues, Debugging, Error handling, Logs analysis	✅	✅	✅	✅
Best Practices	Message design, Queue/topic design, Scaling, Security practices	✅	✅	✅	✅

1. Introduction & Basics

1. What is Solace and what problems does it solve?
2. What are the main messaging patterns supported by Solace?
3. Explain the difference between Pub/Sub and Queue-based messaging.
4. What is a Solace message broker?
5. What are the key use cases for Solace?
6. How does Solace differ from traditional messaging systems?
7. What is event-driven architecture and how does Solace support it?
8. What is the role of topics in Solace messaging?
9. How do queues differ from topics in Solace?
10. What is a VPN in Solace and why is it used?

---

2. Architecture

1. Explain Solace message broker architecture.
2. What are the main components of a Solace broker?
3. How does clustering work in Solace?
4. How is high availability achieved in Solace?
5. What is the role of replication in Solace clusters?
6. How are messages routed in Solace?
7. What are message VPNs?
8. How does Solace handle failover?
9. How does Solace handle load balancing across brokers?
10. What is the Solace event broker?

---

3. Messaging Concepts

1. What is a durable subscription?
2. What is a non-durable subscription?
3. Explain guaranteed messaging in Solace.
4. Explain direct messaging in Solace.
5. What is message acknowledgement?
6. How does Solace handle message ordering?
7. What is message replay in Solace?
8. How do message properties work?
9. How are topics structured in Solace?
10. What are wildcards in topic subscriptions?

---

4. Producers & Publishing

1. How do producers publish messages to Solace?
2. What are the QoS levels for publishing messages?
3. How do message headers and properties work?
4. How to send persistent vs non-persistent messages?
5. How to use the Solace API to send messages?
6. How to implement batching in Solace producers?
7. How to handle message routing errors?
8. How to monitor producer performance?
9. How to send messages to multiple topics?
10. How to integrate producers with Spring Boot?

---

5. Consumers & Subscriptions

1. How do consumers receive messages in Solace?
2. What is the difference between exclusive and shared subscriptions?
3. How to handle durable subscriptions?
4. How to consume messages from queues?
5. How to handle message acknowledgement?
6. How to implement event-driven consumption?
7. How to handle failed message processing?
8. How to monitor consumer performance?
9. How to implement filtering in subscriptions?
10. How to scale consumers in Solace?

---

6. APIs & SDKs

1. Which programming languages are supported by Solace SDKs?
2. How to use the Java API for Solace messaging?
3. How to use the JMS API with Solace?
4. How to use Solace REST messaging?
5. How to use MQTT with Solace?
6. How to publish messages asynchronously?
7. How to receive messages asynchronously?
8. How to handle connection events in APIs?
9. How to implement message listeners?
10. How to integrate Solace APIs with microservices?

---

7. Administration

1. How to configure a Solace broker?
2. How to create and manage message VPNs?
3. How to create and manage users?
4. How to implement ACLs in Solace?
5. How to monitor broker health?
6. How to configure queues and topics?
7. How to manage subscriptions?
8. How to configure persistence stores?
9. How to backup and restore Solace configurations?
10. How to upgrade a Solace broker?

---

8. Security

1. How to implement authentication in Solace?
2. How to implement authorization in Solace?
3. How to configure TLS/SSL for secure messaging?
4. How to encrypt messages in transit?
5. How to implement ACLs for users and applications?
6. How to audit user actions?
7. How to enforce secure client connections?
8. How to rotate certificates in Solace?
9. How to monitor security events?
10. How to integrate Solace security with enterprise IAM?

---

9. High Availability & Reliability

1. How does Solace achieve high availability?
2. What is an active-standby broker setup?
3. How does Solace handle failover between brokers?
4. How does Solace handle message durability during failover?
5. How does Solace replicate messages across clusters?
6. How to test Solace HA configuration?
7. How to monitor failover events?
8. How to configure redundancy groups?
9. How to ensure uninterrupted message delivery?
10. How to implement disaster recovery strategies?

---

10. Performance & Tuning

1. How to optimize message throughput in Solace?
2. How to minimize message latency?
3. How to configure resource limits?
4. How to tune queues for high performance?
5. How to monitor broker resource usage?
6. How to handle large volumes of messages?
7. How to scale Solace brokers horizontally?
8. How to monitor network bandwidth usage?
9. How to configure persistent storage for performance?
10. Best practices for Solace performance tuning.

#MQTT

Last updated    - V4 (16-Sep-2025)

Topic	SubTopic	Basic ✅	Intermediate ✅	Advanced ✅	Expert ✅
Introduction	What is MQTT, Features, Advantages, Use cases	✅	✅	✅	✅
MQTT vs HTTP	Differences, Performance, Use cases	✅	✅	✅	✅
Architecture	Broker, Clients, Publish/Subscribe model	✅	✅	✅	✅
QoS Levels	QoS 0, QoS 1, QoS 2, Message delivery guarantees	✅	✅	✅	✅
Topics & Subscriptions	Topic structure, Wildcards, Hierarchies	✅	✅	✅	✅
Messages	Payload, Retained messages, Duplicate messages	✅	✅	✅	✅
MQTT Broker	Popular brokers, Configuration, Scalability	✅	✅	✅	✅
MQTT Client	Libraries, Connecting, Subscribing, Publishing	✅	✅	✅	✅
Security	Authentication, Authorization, TLS/SSL, Certificates		✅	✅	✅
MQTT with IoT	Integration with IoT devices, Sensors, Real-time updates	✅	✅	✅	✅
Persistent Session	Session state, Clean session, Durable subscriptions		✅	✅	✅
Last Will & Testament	LWT messages, Configuration, Use cases		✅	✅	✅
Retained Messages	Definition, Use cases, Pros & Cons		✅	✅	✅
Advanced Features	MQTT over WebSockets, Bridge, Clustering			✅	✅
Best Practices	Topic naming, QoS selection, Security, Scalability	✅	✅	✅	✅

1. MQTT Basics

1. What is MQTT and why is it lightweight?
2. Explain the publish-subscribe model in MQTT.
3. Difference between MQTT and HTTP protocols?
4. What is a broker in MQTT?
5. What is a client in MQTT?
6. What is a topic in MQTT?
7. What is a subscription?
8. Explain QoS levels in MQTT.
9. Difference between QoS 0, QoS 1, and QoS 2.
10. What is a retained message in MQTT?
11. What is Last Will and Testament (LWT) in MQTT?
12. Explain the use of Clean Session flag.
13. What is persistent session in MQTT?
14. How does MQTT handle offline clients?
15. What is a Keep Alive interval?
16. What are MQTT control packets?
17. What is the maximum payload size in MQTT?
18. Why is MQTT suitable for IoT?
19. Explain MQTT message flow.
20. Difference between synchronous and asynchronous communication in MQTT.
21. What is the CONNECT packet in MQTT?
22. Explain the DISCONNECT process in MQTT.
23. What are wildcards in MQTT topics?
24. Example of single-level vs multi-level wildcard.
25. Advantages and limitations of MQTT.

2. MQTT Protocol Architecture

1. Components of MQTT protocol?
2. Explain the role of broker in MQTT.
3. Role of publishers and subscribers.
4. Explain topic hierarchy in MQTT.
5. What is a topic namespace?
6. Explain MQTT packet structure.
7. What is a fixed header in MQTT packet?
8. What is a variable header in MQTT packet?
9. What is the payload in MQTT packet?
10. Explain PUBLISH packet in MQTT.
11. Explain SUBSCRIBE and SUBACK packets.
12. Explain UNSUBSCRIBE and UNSUBACK packets.
13. What is a PINGREQ packet?
14. What is PINGRESP packet?
15. Explain CONNECT and CONNACK packets.
16. Explain DISCONNECT packet.
17. How does MQTT ensure message delivery?
18. Explain message acknowledgment in QoS 1.
19. Explain message acknowledgment in QoS 2.
20. Duplicate message handling in MQTT.
21. Explain persistent vs non-persistent sessions.
22. What is session expiry in MQTT 5.0?
23. What is topic aliasing in MQTT 5.0?
24. What is shared subscription in MQTT 5.0?
25. What are reason codes in MQTT 5.0?

3. MQTT QoS & Reliability

1. What is QoS in MQTT?
2. Difference between QoS 0, 1, and 2.
3. How does QoS 0 work?
4. How does QoS 1 work?
5. How does QoS 2 work?
6. When should you use QoS 0?
7. When should you use QoS 1?
8. When should you use QoS 2?
9. Explain PUBACK in MQTT.
10. Explain PUBREC, PUBREL, and PUBCOMP packets.
11. Reliability vs performance trade-offs in QoS.
12. How does MQTT handle message duplication?
13. Explain at most once delivery.
14. Explain at least once delivery.
15. Explain exactly once delivery.
16. Can QoS be downgraded between client and broker?
17. What happens if broker crashes mid-delivery?
18. How does QoS interact with retained messages?
19. Performance impact of QoS 2?
20. How to test QoS behavior?
21. Limitations of MQTT QoS mechanism.
22. How does QoS work in clustered brokers?
23. How do different MQTT libraries implement QoS?
24. Role of persistent storage in QoS guarantees.
25. Common pitfalls in using QoS.

4. MQTT Security

1. Is MQTT secure by default?
2. How to secure MQTT communication?
3. Explain TLS/SSL in MQTT.
4. How to authenticate MQTT clients?
5. What are username/password authentication in MQTT?
6. What is token-based authentication?
7. What is certificate-based authentication?
8. What is role-based access control (RBAC)?
9. How to restrict topic access?
10. Difference between authentication and authorization in MQTT.
11. How to secure broker configuration?
12. Common vulnerabilities in MQTT.
13. Man-in-the-middle attack risk in MQTT.
14. How to prevent brute force attacks in MQTT?
15. Importance of TLS mutual authentication.
16. Secure storage of credentials in clients.
17. How to use firewalls with MQTT?
18. How to implement fine-grained permissions?
19. Explain ACLs in MQTT brokers.
20. Security differences between MQTT v3.1.1 and v5.0.
21. Security risks of retained messages.
22. Security implications of Last Will messages.
23. How to audit MQTT systems for security?
24. Best practices for securing MQTT in IoT.
25. Future improvements in MQTT security.

5. MQTT in IoT Use Cases

1. Why is MQTT popular in IoT?
2. Examples of IoT applications using MQTT.
3. Difference between MQTT and CoAP in IoT.
4. MQTT vs AMQP in IoT.
5. How does MQTT work in constrained devices?
6. MQTT in smart home applications?
7. MQTT in industrial IoT (IIoT)?
8. How to use MQTT in healthcare IoT?
9. MQTT in vehicle telematics?
10. How MQTT supports sensor data collection?
11. Role of MQTT in edge computing.
12. Using MQTT with cloud platforms.
13. Integrating MQTT with AWS IoT Core.
14. Integrating MQTT with Azure IoT Hub.
15. Integrating MQTT with Google IoT Core.
16. MQTT in real-time monitoring systems.
17. MQTT in agriculture IoT.
18. MQTT in logistics and supply chain.
19. MQTT for connected wearables.
20. Limitations of MQTT in large IoT systems.
21. MQTT in hybrid IoT systems.
22. Alternatives to MQTT for IoT.
23. MQTT role in low-power IoT networks.
24. Case studies of MQTT in production.
25. Future of MQTT in IoT.

6. MQTT Performance & Scalability

1. How does MQTT handle scalability?
2. How many clients can MQTT support?
3. Factors affecting MQTT performance.
4. How to benchmark MQTT performance?
5. Impact of QoS on performance.
6. Impact of retained messages on performance.
7. Impact of large payloads on performance.
8. Scaling MQTT brokers horizontally.
9. Scaling MQTT brokers vertically.
10. Load balancing techniques in MQTT.
11. Role of clustering in MQTT scalability.
12. Multi-tenant architecture in MQTT.
13. How to tune broker configuration?
14. Optimizing Keep Alive intervals.
15. Reducing latency in MQTT.
16. Handling millions of messages per second.
17. Monitoring MQTT performance.
18. Common bottlenecks in MQTT.
19. Impact of security on performance.
20. MQTT performance in low-bandwidth networks.
21. MQTT vs HTTP performance comparison.
22. MQTT vs WebSocket performance.
23. Performance testing tools for MQTT.
24. Strategies for high availability in MQTT.
25. Future scalability improvements in MQTT.

7. MQTT Brokers

1. What is an MQTT broker?
2. Examples of popular MQTT brokers.
3. Difference between open-source and commercial brokers.
4. What is Eclipse Mosquitto?
5. What is HiveMQ?
6. What is EMQX?
7. What is VerneMQ?
8. What is RabbitMQ MQTT plugin?
9. Features comparison of different brokers.
10. How to choose an MQTT broker?
11. Broker clustering features.
12. Broker load balancing.
13. Broker persistence mechanisms.
14. Broker support for MQTT 5.0.
15. Broker plugin/extension support.
16. Broker monitoring features.
17. Broker security features.
18. Broker scalability limits.
19. Broker deployment models (cloud, on-prem).
20. Broker backup and recovery.
21. Broker high availability setups.
22. Broker support for WebSockets.
23. Broker support for bridging.
24. Broker integration with databases.
25. Broker integration with enterprise systems.

8. MQTT Clients & Libraries

1. Examples of popular MQTT clients.
2. What is Eclipse Paho?
3. What is MQTT.js?
4. What is Eclipse Mosquitto client?
5. What is HiveMQ client library?
6. Client libraries for Python.
7. Client libraries for Java.
8. Client libraries for JavaScript.
9. Client libraries for C/C++.
10. Client libraries for .NET.
11. Client libraries for mobile platforms.
12. Client SDKs for embedded systems.
13. Differences between sync and async clients.
14. MQTT client API structure.
15. How to configure client connection?
16. How to implement reconnection logic?
17. How to implement offline buffering?
18. How to test MQTT clients?
19. Debugging MQTT client issues.
20. Client performance benchmarks.
21. Client limitations in resource-constrained devices.
22. Client-side security features.
23. Client libraries for MQTT 5.0.
24. Client support for WebSockets.
25. Best practices for using MQTT clients.

9. MQTT vs Other Protocols

1. MQTT vs HTTP.
2. MQTT vs CoAP.
3. MQTT vs AMQP.
4. MQTT vs WebSockets.
5. MQTT vs Kafka.
6. MQTT vs DDS.
7. MQTT vs ZeroMQ.
8. MQTT vs OPC-UA.
9. MQTT vs XMPP.
10. MQTT vs LwM2M.
11. Which protocol is best for IoT?
12. Which protocol is best for cloud communication?
13. Which protocol is best for real-time messaging?
14. Advantages of MQTT over HTTP.
15. Limitations of MQTT compared to Kafka.
16. Advantages of MQTT over CoAP.
17. Advantages of MQTT over AMQP.
18. Where MQTT is not suitable?
19. Protocol performance comparison studies.
20. Security comparison between MQTT and AMQP.
21. Scalability comparison between MQTT and Kafka.
22. Reliability comparison between MQTT and CoAP.
23. Latency comparison between MQTT and HTTP.
24. Ease of implementation comparison.
25. Future role of MQTT vs alternatives.

10. Advanced MQTT (v5.0 Features)

1. What is new in MQTT 5.0?
2. Explain reason codes in MQTT 5.0.
3. Explain user properties in MQTT 5.0.
4. What is topic aliasing?
5. What is shared subscription?
6. Explain session expiry interval.
7. What is message expiry?
8. Explain request/response pattern in MQTT 5.0.
9. What is flow control in MQTT 5.0?
10. Explain subscription identifiers.
11. What are enhanced authentication methods?
12. Explain payload format indicator.
13. Explain content type field.
14. Explain response topic in MQTT 5.0.
15. Improvements in error reporting.
16. Differences between v3.1.1 and v5.0.
17. Backward compatibility issues in v5.0.
18. Adoption of v5.0 in brokers.
19. Adoption of v5.0 in client libraries.
20. Benefits of v5.0 over v3.1.1.
21. Challenges in migrating to MQTT 5.0.
22. Real-world use cases of MQTT 5.0.
23. Limitations of MQTT 5.0.
24. Performance impact of new features.
25. Future improvements beyond MQTT 5.0.