UST Senior Systems Analyst and Technical Lead Interview Questions and Answers

Singleton pattern can break due to serialization, reflection, and cloning; here's how to resolve these issues.

• 1. **Serialization**: Use the 'readResolve' method in Java to ensure the singleton instance is returned during deserialization.

• Example: Implement 'readResolve' in your singleton class to return the existing instance.

• 2. **Reflection**: Prevent instantiation via reflection by throwing an exception in the const...read more

ConcurrentHashMap is a thread-safe implementation of Map interface in Java.

• ConcurrentHashMap allows multiple threads to read and write concurrently without blocking each other.

• It internally divides the map into segments and locks each segment separately to allow concurrent access.

• Other synchronized structures like Hashtable and synchronizedMap lock the entire map, causing performance issues.

• ConcurrentHashMap is preferr...read more

Immutable class with List/Date Type property

• Create a final class with private final fields

• Use unmodifiableList() to create immutable List

• Use defensive copying for Date property

• No setters, only getters

• Override equals() and hashCode() methods

To make a singleton class thread safe, use synchronized keyword or double-checked locking. Volatile keyword ensures visibility of changes across threads.

• Use synchronized keyword to ensure only one thread can access the instance at a time

• Use double-checked locking to avoid unnecessary synchronization

• Declare the instance variable as volatile to ensure visibility of changes across threads

• Example: public static synchronize...read more

Stream, Lambda and Functional interface can be combined to write functional programming in Java

• Streams provide a functional way to process collections of data

• Lambda expressions allow for functional programming by providing a way to pass behavior as an argument

• Functional interfaces define the contract for a lambda expression

• Example: using a stream to filter a list of integers and then using a lambda expression to map ea...read more

To access rest endpoint in asynchronous manner, use AJAX or fetch API with async/await or promises.

• Use AJAX or fetch API to make asynchronous requests to the REST endpoint

• Use async/await or promises to handle the asynchronous response

• Ensure that the endpoint supports asynchronous requests

Static methods are useful for utility functions but can't access instance variables.

• Advantage: Can be called without creating an instance of the class

• Advantage: Useful for utility functions that don't require access to instance variables

• Disadvantage: Can't access instance variables

• Disadvantage: Can't be overridden in subclasses

Helm is a package manager for Kubernetes while Kubernetes is an open-source container orchestration platform.

• Helm is used to manage Kubernetes applications and their dependencies

• Helm charts are used to define, install, and upgrade Kubernetes applications

• Kubernetes is used to automate deployment, scaling, and management of containerized applications

• Kubernetes uses declarative configuration to manage applications and the...read more

NoSql is sufficient when data is unstructured and requires high scalability and performance.

• Consider the type of data and its structure

• Evaluate the scalability and performance requirements

• Assess the need for complex queries and transactions

• Examples: social media data, IoT data, real-time analytics

In Cassandra, leaders are responsible for handling read and write requests while followers replicate data.

• Leaders are chosen based on their proximity to the client and their ability to handle requests efficiently.

• Followers replicate data from the leader and can take over as leader if the current leader fails.

• Cassandra uses a gossip protocol to ensure that all nodes are aware of the current leader and follower status.

• Le...read more

AWS CLI commands used as Senior Systems Analyst and Technical Lead

• aws s3 ls - List all S3 buckets

• aws ec2 describe-instances - Describe all EC2 instances

• aws rds describe-db-instances - Describe all RDS instances

• aws lambda list-functions - List all Lambda functions

• aws cloudformation describe-stacks - Describe all CloudFormation stacks

To make a db entity unmodifiable, use constraints or triggers to prevent updates or deletes.

• Use a constraint to prevent updates or deletes on the entity

• Create a trigger to roll back any update or delete operation on the entity

• Grant read-only access to the entity to prevent modifications

• Use database permissions to restrict modification access to the entity

• Consider using a separate read-only database for the entity

Spring Data supports various repositories for different data sources

• Spring Data JPA for relational databases

• Spring Data MongoDB for NoSQL databases

• Spring Data Redis for key-value stores

• Spring Data Cassandra for column-family stores

• Spring Data Neo4j for graph databases