---
title: '05 AWS Route 53'
disqus: hackmd
---

:::info
AWS Certified Developer Associate DVA-C01
:::

05 AWS Route 53
===

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## Table of Contents

[TOC]

Route 53
---
- route53 is managed dns (domain name system)
- dns is collection of rules and records which helps clients understand how to rch server through URLs
- in aws most common records are
- A
- hostname to ipv4
- AAAA
- hostname to ipv6
- CNAME
- hostname to hostname
- alias
- hostname to aws res
- route53 can use
- public domain names you own/bought
- priv domain names that can be resolved by your instances in your VPCs
- has advanced features like
- load balancing
- through dns
- AKA client lb
- health checks
- but limited
- routing policy
- simple
- failover
- geolocation
- latency
- weighted
- multi value
- pay $0.50 per month per hosted zone


### DNS Records TTL
- high ttl
- Eg. 24h
- less traffic on dns
- possibly outdated records
- ttl need to end before change applied
- low ttl
- Eg. 60s
- more traffic on dns
- records outdates for less time
- easy to change record
- ttl is mandatory for ea dns record


### CNAME vs Alias
- aws res (Eg. load balancerm cloudfront etc.) exposes an aws hostname
- CNAME
- points hostname to any other hostname
- Eg. app.mydomain.com => blabla.anything.com
- __only for non root domain__
- alias
- points hostname to aws res
- Eg. app.mydomain.com => blabla.amazonaws.com
- works for root/non root domains
- free
- native health check
- NOTE
- exam ask diff between cname and alias
- root domain = alias, non root = cname or alias
- but shld be alias anyways cuz pt to aws service and is free

### Health Checks
- have x health checks failed = unhealthy
- default 3
- after x health checks passed = healthy
- default 3
- default health check interval = 30s
- can set to 10s
- but higher cost
- AKA fast health check
- about 15 health checkers checks endpt health
- 1 req every 2 secs on average
- if interval lesser, avg go up
- can have http, tcp and https health checks
- no ssl verification
- possibility of integrating health check with cloudwatch
- can be linked to route53 dns queries

### Route53 as a Registrar
- domain name registrar - org that manages reservation of internet domain names
- famous names
- godaddy
- google domains
- etc.
- NOTE
- domain registrar != DNS
- but ea registrar usually comes with some DNS features

#### 3rd Party Registrar with Route53
- if buy domain on 3rd pt website, can still use route53
- create hosted zone in route53
- update NS records on 3rd pt website to use route53 name servers

### Console
- is global service

- need buy avail domain name
- check personal info to do purchase

- after create domain name, can click on it to add some records

- create record set

#### TTL
- default 300sec (5mins)

#### Health Checks
- what to monitor
- specify endpt


Route53 Routing Policies
---
### Simple Routing Policy
- maps hostname to another hostname
- use when need to redirect to single res
- cannot attach health checks to simple routing policy
- if multiple values returned, random one chosen __by client__


### Weighted Routing Policy
- control % of requests that go to specific endpt
- Eg. helpful to test 1% of traffic on new app ver
- helpful to split traffic between 2 regions
- can be associated with health checks
- if 1 instance not working properly, no traffic sent to it


### Latency Routing Policy
- redirect to server that has least latency close to us
- super helpful when latency of users is priority
- latency is evaluated in terms of user to designated aws region
- Eg. germany can be directed to US if its lowest latency


### Failover Routing Policies
- secondary only used when pri fails
- route53 will have mandatory health check for pri associated with pri record
- auto failover to sec if check fails

- must associate with health check if pri
- will give error if put no

### Geolocation Routing Policy
- diff from latency based
- routing based on user location
- Eg. specify traffic from UK go to xx ip
- shld create default policy in case no match on location


### Multi Value Routing Policy
- use when routing traffic to multiple res
- want to associate route53 health checks with records
- up to 8 healthy records returned for ea multi value query
- multi value is not substitute for ELB
- but still do some kind of lb on client side
- NOTE
- some sort of improvement from simple routing policy


- ttl will update for all multi value

- if u dig the dns record it should return more than 1 answers

###### tags: `AWS Developer Associate` `Notes`