Explain how AWS DMS works.
AWS DMS operates by setting up a temporary replication server that reads data from the source and writes it to the destination.
1. Replication Instance
When you start a migration, AWS provisions a managed EC2 instance in the background called the Replication Instance. This instance performs the heavy lifting—connecting to your source, reading the data, formatting it, and loading it into the target.
2. Endpoints (Source and Target)
DMS needs to know exactly where to connect. You define two endpoints:
- Source Endpoint: The database you are moving away from (can be on-premises, on an EC2 instance, or in another cloud).
- Target Endpoint: The destination database inside AWS (e.g., Amazon RDS, Aurora, Amazon S3, or DynamoDB).
3. Replication Tasks
A DMS Task defines exactly how the data moves. You can choose from three types of migration styles:
- Full Load: Migrates all existing data from the source to the target at that specific point in time.
- Change Data Capture (CDC): Captures ongoing changes (Inserts, Updates, Deletes) in real-time by reading the source database's transaction logs.
- Full Load + CDC: The most common method. It copies the entire bulk database first, and then seamlessly transitions into capturing live changes. This keeps both databases in sync until you are ready to switch your application to the new AWS database.
What are the considerations for choosing an instance type in EC2?
When choosing an Amazon EC2 instance type, you need to match your application's technical demands with your budget.
Here are the core considerations grouped by category:
1. Workload Requirements (Instance Families)
2. CPU Performance & Burstability
3. Processor Architecture
4. Storage & Network Throughput
5. Cost & Pricing Models
How can you implement disaster recovery in AWS?
Use AWS Elastic Disaster Recovery (AWS DRS)
- Install the AWS Replication Agent on your primary servers (EC2, on-premises VMs, or other clouds).
- AWS DRS will continuously replicate your servers block-by-block into a low-cost staging area in your DR region.
- In a disaster, click "Initiate Recovery" in the AWS DRS console. It will automatically launch fully functional EC2 instances from the staging area within minutes.
You accidentally deletes important data stored in an EFS file system. How can you recover the lost data?
You recover lost EFS data by restoring from an AWS Backup recovery point, using either a full restore or an item‑level restore, with all restored files placed in a special aws‑backup-restore_ directory* under the EFS root.
In short: AWS Backup is the supported mechanism for EFS data recovery. Restores are non‑destructive and always write recovered data into a new recovery directory rather than overwriting existing paths
How can you optimize the cost of using AWS EFS without impacting performance?
The most effective way to cut EFS costs without hurting performance is to combine lifecycle tiering (Standard → IA/Archive) with the right throughput mode (Elastic for most workloads) while keeping General Purpose performance mode and recommended NFS settings for high throughput and low latency.
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