Paytm Interview Experience for Senior Software Engineer | 4 Years Experienced
Technical Round(1 hr):
- Asked about my current company projects and techstack used
- what is thread? Synchronized keyword? Diff. ways of creating threads in java, which one is better? difference b/w multithreading & multiprogramming
- What is txn in DBMS? ACID properties
- Internal implementation of map. How put of HashMap works? https://www.javatpoint.com/working-of-hashmap-in-java
- Reverse singly linked list. Also write recursive code (https://www.w3wiki.net/recursively-reversing-a-linked-list-a-simple-implementation/)
- https://www.w3wiki.net/detect-and-remove-loop-in-a-linked-list/
- https://www.w3wiki.net/sort-an-array-of-0s-1s-and-2s/
- https://www.w3wiki.net/design-a-stack-that-supports-getmin-in-o1-time-and-o1-extra-space/
- Write code for singleton class and make it thread safe.
Technical Round(1 hr):
- What is inheritance? Give an example
- Function overloading and overriding
- Static func. related question
Java
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"
);
}
}
- SOLID principles
- HashMap and HashSet in java. How they work?
- How Garbage Collector works? When it is called and how can we call it explicitly? (https://www.tutorialspoint.com/how-can-we-call-garbage-collection-gc-explicitly-in-java)
- https://www.w3wiki.net/minimum-cost-to-reach-from-the-top-left-to-the-bottom-right-corner-of-a-matrix/
- Which design patterns are used by you? Explain observer pattern. Also, Tell scenario where Singleton pattern was used in your project.
- https://www.w3wiki.net/maximum-size-rectangle-binary-sub-matrix-1s/
- Difference b/w abstract class and interface. Why both are required? Can abstract class have constructors?
- How can we make a variable immutable in java? Is it possible to modify final variable value?
Technical Round(1 hr):
- Adv. and disadv. of indexing
- 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?
- Isolation levels in SQL.
- Public key, private key, cryptography.
- Diff b/w MongoDB and SQL
- HAshMap put() and get() complexity
- Time complexity of following code:
Java
int
fib(
int
n) {
if
(n ==
0
|| n ==
1
) {
return
n;
}
return
fib(n-
1
) + fib(n-
2
);
}
- https://www.w3wiki.net/maximize-sum-of-k-elements-in-array-by-taking-only-corner-elements/
- What are features of spring and spring boot?
- Do you know about Redis?
- what is HTTP and HTTPS?
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