IT-Exam-AWS

Core AWS Services

• EC2 (Elastic Compute Cloud): Virtual servers in the cloud.
• S3 (Simple Storage Service): Object storage for any type of file (images, backups, videos, logs).
• ELB (Elastic Load Balancer): Distributes traffic across multiple EC2s or containers.
• Database RDS (Relational Database Service): Managed relational database (e.g., MySQL, PostgreSQL).
• Database DynamoDB: Managed Serverless and NoSQL database (key-value or document-based) to handles fast session data.
• Lambda: Run code without servers. For serverless scenarios.
• CloudFront: AWS’s Content Delivery Network (CDN) to reduce latency (edge server).
• IAM (Identity and Access Management): Controls who can do what in your AWS account. (roles, policies, least privilege).

Architecture Best Practices

• Operational Excellence
• Security
• Reliability
• Performance Efficiency
• Cost Optimization
• Sustainability (recent addition)

Low-Latency Architecture

• Use CloudFront for global distribution
• Place backend services in multiple Availability Zones
• Use Auto Scaling for EC2 or Lambda
• Use Elasticache for caching (Redis/Memcached)
• Choose regions close to the end users
• Use Global Accelerator if needed

Databases

Amazon RDS (Relational Database Service) & Aurora

• You need structured data with relationships (foreign keys, joins).
• Your application depends on SQL queries (PostgreSQL, MySQL, MariaDB, SQL Server, Oracle).
• You require ACID transactions (Atomicity, Consistency, Isolation, Durability).
• You need complex reporting or analytics using joins, aggregations, etc.

Amazon DynamoDB (NoSQL,MongoDB, CouchDB, DynamoDB)

• You need high-speed reads/writes at any scale
• You don’t need complex relationships (no joins)
• Your data is semi-structured or unstructured (Schema-less or flexible schema)
• You expect massive scale (e.g., millions of users, IoT, gaming)
• High scalability: Designed to scale horizontally across servers
• Prioritizes performance, scalability, availability over strict consistency

Techo

ACID (Atomicity, Consistency, Isolation, Durability) transactions

• A (Atomicity): A transaction is all or nothing — if one part fails, the entire thing rolls back.
• C (Consistency): The database must move from one valid state to another — rules and constraints are respected.
• I (Isolation): Transactions don't interfere with each other — even when run at the same time.
• D (Durability): Once a transaction is committed, the data is permanently saved, even if the system crashes.

ACID-Example

Let’s say you’re transferring $100 from Account A to Account B.

• Subtract $100 from Account A
• Add $100 to Account B

For it to be an ACID-compliant transaction, both steps must happen together, or neither should.

Here’s how each ACID property applies:

• Atomicity: If step 1 succeeds but step 2 fails — rollback step 1.
• Consistency: The total balance in the system must remain the same.
• Isolation: Another transfer happening at the same time won't mess this one up.
• Durability: Even if the server crashes right after the transfer — the change will persist.

In AWS Context:

• RDS: Fully supports ACID across all supported engines.
• DynamoDB: Supports transactional APIs, but not as flexible as RDS for complex multi-table transactions.

CDN (Content Delivery Network)

• CloudFront is AWS’s CDN
• is a geographically distributed network of servers that cache and deliver content to users based on their location.
• Instead of all users fetching content from a single origin server (e.g., in Frankfurt), the CDN brings the content closer to the user
  • Edge Locations
  • Caching
  • Dynamic Content Optimization
  • Global Load Balancing

Elastic Load Balancer

• An Elastic Load Balancer (ELB) automatically distributes incoming traffic across multiple targets (like EC2 instances, containers, or IPs) in one or more Availability Zones (AZs).
• Goal:
  • Prevent any single server from getting overwhelmed,
  • Ensure high availability,
  • And handle traffic dynamically as demand changes.

S3 (scalable object storage service)

• A scalable object storage service used to store and retrieve any amount of data — like images, videos, backups, logs, documents, etc.
• Storage Classes:
  • S3 Standard: Frequently accessed data
  • S3 Intelligent-Tiering: Automatic tiering based on access patterns
  • S3 Standard-IA: Infrequent Access (e.g., backups)
  • S3 One Zone-IA: Infrequent access, one AZ only
  • S3 Glacier/Deep Archive: Archival, long-term storage (e.g., compliance)