1. Route 53

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1️⃣ What is Route 53?

• Amazon Route 53 is a scalable DNS (Domain Name System) service

• It translates:

  google.com → 142.250.xxx.xxx (IP address)
  

• Named Route 53 because:

  • “Route” → traffic routing
  • “53” → DNS uses port 53

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2️⃣ Core Functions of Route 53

📌 1. Domain Registration

• Buy and manage domain names
  • Example: om-mapari.com (btw i use cloudflare for dns)

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📌 2. DNS Routing

• Maps domain → IP / resource
• Works with:
  • EC2
  • S3
  • Load Balancer
  • CloudFront

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📌 3. Health Checking

• Monitors endpoints
• Routes traffic only to healthy resources

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3️⃣ Key Components

📌 Hosted Zones

• A container for DNS records
• Types:
  • Public Hosted Zone → internet-facing 🌍
    • Accessible over internet
    • Used for Websites
  • Private Hosted Zone → inside VPC 🔒
    • Works inside VPC only
    • Used for
      • Internal microservices
      • Example: db.internal → private IP inside VPC

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📌 DNS Records

Record Type	Purpose
A Record	Domain → IPv4 address
CNAME	Domain → another domain
Alias	AWS resource mapping (LB, S3, etc.)
NS	Name servers (DNS resolution)
SOA	Start of Authority (metadata, rarely used)
AAAA	Domain → IPv6

📌 Important:

• NS record → resolves domain
• A/CNAME → routes traffic to resource

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📌 Alias Record (Important ⭐)

• AWS-specific
• Points to:
  • ELB
  • CloudFront
  • S3
• Benefits:
  • No cost
  • Supports root domain (example.com)

📌 Step-by-step setup if you buy domain from other registrar :

1. Buy domain from registrar (GoDaddy, Google Domains, etc.)
2. Create Hosted Zone in Route 53
3. Copy AWS Name Servers (NS records)
4. Replace registrar DNS with AWS NS
5. 📌 Key: Always use Route 53 NS, not registrar default NS

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4️⃣ Routing Policies (VERY IMPORTANT 🔥)

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📌 1. Simple Routing

• Flow: User → Route 53 → A Record → EC2 IP
• Steps:
  • Create A record
  • Point to EC2 public IP
• Problem:
  • IP is static → breaks if instance changes

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📌 2. Weighted Routing

• Distributes traffic based on percentage

Server A → 70%
Server B → 30%

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📌 3. Failover Routing

• Primary + Secondary setup If primary fails → switch to backup
• 📌 Flow:
  • If Primary works → serve traffic
  • If Primary fails → switch to Secondary
• Use cases:
  • Disaster recovery
  • High availability

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📌 4. Geolocation Routing

• Route traffic based on user location (country)
• Example:
  • India → Server A
  • US → Server B
• Use cases:
  • Region-specific content
  • Compliance (data locality)

India → Indian server
US → US server

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5️⃣ TTL (Time To Live)

• Time DNS record is cached
• Example:
  • TTL = 300 sec
• Lower TTL:
  • Faster updates ⚡
  • More DNS queries

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6️⃣ Alias vs CNAME

Feature	Alias	CNAME
AWS-specific	✅	❌
Root domain supported	✅	❌
Cost	Free	Charged
Target	AWS resources	Domain only

📌 Example:

• om-mapari.com → Alias (works)
• om-mapari.com → CNAME (❌ not allowed)

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7️⃣ Domain Resolution Flow (VERY IMPORTANT 🔥)

Add this for strong fundamentals:

User → Local DNS cache  
     → ISP DNS  
     → Root DNS  
     → TLD (.com)  
     → Route 53 NS  
     → A Record  
     → IP → Server

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8️⃣ Real-World Architecture (Nice Add-on)

User  
 ↓  
Route 53 (DNS)  
 ↓  
CloudFront (CDN)  
 ↓  
Load Balancer  
 ↓  
EC2 / ECS / Lambda

9️⃣ Pricing Basics

• Charged for:
  • Hosted zones
  • DNS queries
  • Health checks
• Domain registration extra

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