Interview Q&A / AWS & Cloud

1. What is a VPC, and what is the difference between public and private subnets?

   A VPC is your own private network inside AWS. A public subnet has a route to an internet gateway, so resources with public IPs can be reached from the internet. A private subnet has no such route; its servers reach the internet only outbound, through a NAT gateway placed in a public subnet.

   IntermediateIn-depth4 min read
2. What is the difference between a security group and a network ACL in AWS?

   A security group is a stateful firewall attached to an instance's network interface, with allow rules only. A network ACL is a stateless firewall on a subnet, with numbered allow and deny rules checked in order. Because NACLs are stateless, you must allow return traffic explicitly, usually on ephemeral ports.

   IntermediateIn-depth4 min read
3. What is the difference between RDS and DynamoDB, and when would you use each?

   RDS is a managed relational database service running engines like MySQL or PostgreSQL, with SQL, joins and transactions. DynamoDB is a serverless key-value and document database that gives fast, predictable performance at very large scale if you design around known access patterns. Use RDS for relational data and flexible queries; use DynamoDB for simple, high-volume lookups by key.

   IntermediateIn-depth4 min read