session-11.txt

A 	 -> IPv4
AAAA -> IPv6
MX 	 -> Mail
NS	 -> Domain authority
CNAME -> Point to another domain
TXT  -> verification

1XX -> informational
2XX -> Success
3XX -> Redirectional
4XX -> Client error
5XX -> Server error

NoSQL
=======
data is un sctructured
useful when huge amounts of data
data is stored as documents
generally used for product catalouges, Real-time analytic, etc but not for transactions

Redis
=======
in-memory(RAM) database
in-memory(RAM) database
HD -> RAM -> Processor
key-value database
apps -> cache -> database

Asynchronous
===========
ActiveMQ, IBM MQ, RabbitMQ, Kafka, etc...

request and wait -> http
fire and forget  -> mail, whatsapp, etc..

Prodcuer -> Who is sending message
Consumer -> Who is consuming message

No waiting, good user experience
Scalability
Reliability
Loose Coupling
	Tight Coupling -> with on our system
Queue management -> FIFO

Pub/Sub -> 1 to many
Queue -> 1 to 1
Publisher -> Who is sending message
Subscriber -> Who is following

Generally databases by default not accept connections from remote servers

backend -> combining all components in single module

component == module == application
node == box == server

useradd --system --home /app --shell /sbin/nologin --comment "roboshop system user" roboshop

/home/user-name

frontend

/api/catalogue -> forward those requests to catalogue component

Jan 22 02:58:54 ip-172-31-78-60.ec2.internal catalogue[2349]: {"level":"info","time":1769050734046,"pid":2349,"hostname":"ip-172-31-78-60.ec2.internal","req":{"id":42,"method":"GET","url":"/product/RMC","headers":{"host":"catalogue.daws88s.online:8080","connection":"close","accept":"application/json, text/plain, */*","user-agent":"Mozilla/5.0 (iPhone; CPU iPhone OS 26_1_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/144.0.7559.85 Mobile/15E148 Safari/604.1","accept-language":"en-IN,en;q=0.9","referer":"http://daws88s.online/product/RMC","accept-encoding":"gzip, deflate"},"remoteAddress":"::ffff:172.31.78.82","remotePort":44312},"res":{"statusCode":200,"headers":{"x-powered-by":"Express","timing-allow-origin":"*","access-control-allow-origin":"*","content-type":"application/json; charset=utf-8","content-length":"198","etag":"W/\"c6-sTc8wmePzqQNogwimig6Jch9Qj4\""}},"responseTime":4,"msg":"request completed","v":1}


[Unit]
Description = Cart Service
[Service]
User=roboshop
// highlight-start
Environment=REDIS_HOST=redis.daws88s.online
Environment=CATALOGUE_HOST=catalogue.daws88s.online
Environment=CATALOGUE_PORT=8080
// highlight-end
ExecStart=/bin/node /app/server.js
SyslogIdentifier=cart

[Install]
WantedBy=multi-user.target