Tech Lead Mock Interview

Notes

  • ask programming questions
  • ask react & js

Questions

  1. How do you merge two fields in DB that has alread have data…and need to performa the same operation in all the environments.
    • eg: first_name, last_name => full_name need to do in dev, test, staging, prod
    • Ans: DB Migration libraries
  2. Symmetric Encryption vs Asymetric Encryption
    • when we will use …give examples

  3. in JWT…when to use Secret & when to use public key - private keys

  4. Hashing vs Encrytion

  5. How to store secure data in DB…even developer should not see
    • it should be searchable & retrivable
    • Ans:- use two files for one value
    • eg:- email => email_encrypted ( to retieve ), email_hashed ( to search )
  6. Saga pattern vs Event Driven Architecture…when to use them
    • Saga is one of Event Driven Architecture with Transaction Managamente
      • Rollback feature

  7. what is 2PC ( 2 Phase Commit )

  8. How logout is handled in micro server ( OAuth2 )

  9. OAuth2 vs OpenId Connect vs OAuth2 + OpenId Connect

Programming Questions

  • Find the pair of numbers whose sum is equal to the given from a given array.
    • Eg:- 8, [1,2,8,3,4,5,6,7] → 1,7 : 2,6 : 3,5
    • Hint: Binary Search
  • Find Equilibrium index in a given array
    • eg: [0,1,2,3,4,0,2] => at index 3, left side elements sum = right side elements sum

  • Find the first non-repeating element in an array without using map

  • Find the kth largest element in an unsorted array (QuickSelect / Heap)

Solutions

  • Binary Search

     public class BinarySearch {

  public static int binarySearch(int[] arr, int target) {

      int left = 0;
      int right = arr.length - 1;

      while (left <= right) {

          int mid = left + (right - left) / 2;

          if (arr[mid] == target)
              return mid;

          if (arr[mid] < target)
              left = mid + 1;
          else
              right = mid - 1;
      }

      return -1;
  }

  public static void main(String[] args) {

      int[] arr = {1,2,3,4,5,6,7,8};

      System.out.println(binarySearch(arr, 6));
      }
  }

    Recursion

       public class BinarySearch {

  static int search(int[] arr, int left, int right, int target) {

      if (left > right)
          return -1;

      int mid = left + (right - left) / 2;

      if (arr[mid] == target)
          return mid;

      if (arr[mid] < target)
          return search(arr, mid + 1, right, target);

      return search(arr, left, mid - 1, target);
  }

  public static void main(String[] args) {

      int[] arr = {1,2,3,4,5,6,7};

      System.out.println(search(arr, 0, arr.length - 1, 6));
   }
 }

  • First Non-repeating element in an array without using map

     public class FirstNonRepeating {

  public static int firstNonRepeating(int[] arr) {

      for (int i = 0; i < arr.length; i++) {

          boolean repeating = false;

          for (int j = 0; j < arr.length; j++) {

              if (i != j && arr[i] == arr[j]) {
                  repeating = true;
                  break;
              }
          }

          if (!repeating) {
              return arr[i];
          }
      }

      return -1;
  }

  public static void main(String[] args) {

      int[] arr = {4, 5, 1, 2, 0, 4, 1, 2};

      System.out.println(firstNonRepeating(arr));
      }
  }

  • Kth Largest element

    • sort the array…and take kth element