ACKO SDE (Software Development Engineer) Interview Questions and Answers

Q1. It was an MCQ Round and the questions were a mixture of CS fundamentals topics.
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This round contained 2 coding questions.

Q1. This was a one on one coding round where I was asked 3 questions that were of Easy to Medium level of LeetCode.
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Q1. HR round was more of a technical interview round where I was asked about my android projects and some core android topics since both me and my interviewer were Android Developers.
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Q1. Number of Islands
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Count the number of islands in a 2D grid.
• Iterate through the grid and for each '1', perform a depth-first search to mark all connected '1's as visited.

• Increment the count of islands for each new '1' encountered.

• Return the total count of islands.
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Q2. Coin change problem
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The coin change problem involves finding the minimum number of coins needed to make a certain amount of change.
• Use dynamic programming to solve the problem efficiently

• Start with a base case where the amount of change is 0

• Iterate through each coin denomination and calculate the minimum number of coins needed for each amount of change

• Store the results in a table and use them to calculate the minimum number of coins for l
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Q1. Javascript based questions
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Q1. Discussion with a senior manager
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Basic puzzles of medium complexity level. No improvement required

DSA questions of easy level. Asked for memory optimisations.

Q1. High level system design of wallet payment system, took example of paytm. This was hld questions so just basic components
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Q1. Low level system design of parking lot system
Ans. 
Design a parking lot system at a low level
• Divide system into components like parking spots, ticketing system, payment system

• Implement data structures like queues for managing parking spots

• Use algorithms like least recently used for spot allocation

• Consider scalability and performance in design
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Q2. Review of one of my projects at past company
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75 min test with 18 Java theory questions

Q1. Synchronized keyword usage
Ans. 
The synchronized keyword in Java is used to control access to shared resources in a multithreaded environment.
• Synchronized keyword can be used to synchronize access to critical sections of code to prevent race conditions.

• It can be applied to methods or code blocks to ensure only one thread can access them at a time.

• Example: synchronized void myMethod() { // code }

• Example: synchronized(this) { // code }
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Q2. Message Queue types
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Q3. Thread Contention
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Q4. Java Profiling Tools
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Q5. Abstract classes
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Q1. What is collection framework?
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Collection framework is a unified architecture for representing and manipulating collections of objects in Java.
• It provides interfaces (like List, Set, Map) and classes (like ArrayList, HashSet, HashMap) to store and manipulate groups of objects.

• It allows for easy manipulation, sorting, searching, and iteration of collections.

• Collections in the framework can store objects of any type, including user-defined classes.

• Exa...read more
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Q2. What is spring boot dependency injection?
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Spring Boot dependency injection is a design pattern where objects are passed their dependencies rather than creating them internally.
• In Spring Boot, dependency injection is achieved through the use of @Autowired annotation.

• It helps in achieving loose coupling between classes and promotes easier testing and maintenance.

• Example: @Autowired private UserService userService; // Injecting UserService dependency
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Q3. What is the use of rate limiter?
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Rate limiter is used to control the rate of incoming requests to a server or API.
• Prevents server overload by limiting the number of requests a client can make in a specific time period

• Helps protect against DDoS attacks by limiting the rate of incoming requests

• Ensures fair usage of resources by preventing one client from monopolizing server resources

• Can be implemented using algorithms like token bucket or leaky bucket

• Ex...read more
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Q4. What is the mean by thread, how many ways we can create thread?
Ans. 
A thread is a lightweight sub-process that allows concurrent execution within a process. Threads can be created in multiple ways.
• Threads can be created by extending the Thread class in Java.

• Threads can be created by implementing the Runnable interface in Java.

• Threads can be created using thread pools in Java.

• Threads can be created using asynchronous functions in JavaScript.
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Q5. What is use of thread.join()?
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thread.join() is used to wait for a thread to finish its execution before moving on to the next steps.
• thread.join() blocks the current thread until the thread it is called on completes its execution.

• It is commonly used in multi-threaded applications to ensure that all threads have finished before proceeding.

• Without thread.join(), the main thread may continue executing while other threads are still running.

• Example: thre...read more
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Q6. What is the difference between sync and asynchronous call?
Ans. 
Sync call blocks the execution until the response is received, while asynchronous call allows the program to continue executing without waiting for the response.
• Sync call blocks the program execution until the response is received

• Asynchronous call allows the program to continue executing without waiting for the response

• Sync calls are easier to understand and debug, but can lead to performance issues if used excessively

• ...read more
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Q7. How to deploy your service in production server?
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Deploying service in production server involves building the application, configuring the server, and monitoring performance.
• Build the application code into a deployable package (e.g. JAR file for Java applications)

• Configure the production server with necessary dependencies and environment variables

• Deploy the application package to the server using tools like Docker, Kubernetes, or manual deployment scripts

• Monitor the ...read more
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Q8. What is use of Jenkins and kubernates?
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Jenkins is a continuous integration tool used for automating software development processes, while Kubernetes is a container orchestration platform for managing containerized applications.
• Jenkins is used for automating the building, testing, and deployment of software projects.

• Kubernetes helps in automating the deployment, scaling, and management of containerized applications.

• Jenkins can be integrated with Kubernetes t...read more
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Q9. What is the difference between fail safe and fail fast
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Fail safe focuses on ensuring system stability and preventing catastrophic failures, while fail fast prioritizes quick detection and response to errors.
• Fail safe is about designing systems to minimize the impact of failures and ensure stability.

• Fail fast is about quickly detecting and responding to errors to prevent further issues.

• Fail safe often involves redundancy and error checking mechanisms to prevent catastrophic...read more
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Q1. One leetcode easy-medium problem
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Q2. Java, springboot and oops question
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Q1. Project related questions
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Q2. System design questions
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It was more based on array/string manipulation, stack/queue based, if you have solved questions before then it will be easy/medium difficulty level for yo

Q1. Asteroid collision
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Q2. Stack/queue based
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Q1. Resume based discussion. therory concepts/ OOPS's , DBMS, OS,etc
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Q1. Explain Concurrency
Ans. 
Concurrency is the ability of a system to execute multiple tasks simultaneously.
• Concurrency allows multiple tasks to run concurrently, improving performance and efficiency.

• Concurrency can be achieved through multithreading or multiprocessing.

• Example: A web server handling multiple requests simultaneously using multithreading.
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Q2. Explain Acid principles
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ACID principles are a set of properties that guarantee database transactions are processed reliably.
• Atomicity: Transactions are all or nothing. If one part of the transaction fails, the entire transaction is rolled back.

• Consistency: Transactions bring the database from one valid state to another. All constraints are satisfied.

• Isolation: Transactions are isolated from each other until they are completed.

• Durability: Once...read more
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