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Paytm Interview Experience for Senior Software Engineer | 4 Years Experienced

Last Updated : 16 Jun, 2021
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Technical Round(1 hr):

  1. Asked about my current company projects and techstack used
  2. what is thread? Synchronized keyword? Diff. ways of creating threads in java, which one is better? difference b/w multithreading & multiprogramming
  3. What is txn in DBMS? ACID properties
  4. Internal implementation of map. How put of HashMap works?
  5. Reverse singly linked list. Also write recursive code (
  9. Write code for singleton class and make it thread safe.

Technical Round(1 hr):

  1. What is inheritance? Give an example
  2. Function overloading and overriding
  3. Static func. related question


    class MyBase{
    public static void func(){
     System.out.println("Base static called");
    class MyDerived extends MyBase{
    public void func(){                // is this allowed?
     System.out.println("Derived static called");


  4. SOLID principles
  5. HashMap and HashSet in java. How they work?
  6. How Garbage Collector works? When it is called and how can we call it explicitly? (
  8. Which design patterns are used by you? Explain observer pattern.  Also, Tell scenario where Singleton pattern was used in your project.
  10. Difference b/w abstract class and interface. Why both are required? Can abstract class have constructors?
  11. How can we make a variable immutable in java? Is it possible to modify final variable value?

Technical Round(1 hr):

  1. Adv. and disadv. of indexing
  2. A db Table having  100 Million rows, A B C are 3 columns

    A -> 1000 Unique values   B -> 1 Million Unique Values   C -> 10 Million Unique Values

    query made oftenly on db-> “select * from T where A = ? and B = ? and C = ?”

    How we should create indexes in the table? Can’t we create composite indexes on A,B?

  3. Isolation levels in SQL.
  4. Public key, private key, cryptography.
  5. Diff b/w MongoDB and SQL
  6. HAshMap put() and get() complexity
  7. Time complexity of following code:


    int fib(int n) {
       if (n == 0 || n == 1) {
           return n;
       return fib(n-1) + fib(n-2);


  9. What are features of spring and spring boot?
  10. Do you know about Redis?
  11. what is HTTP and HTTPS?

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