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Important_terms.md

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Important Ports

Normal ports:

FTP: 21 SSH: 22 RDP: 3389 SFTP: 22 (same as SSH) HTTP: 80 HTTPS: 443

RDS Databases ports:

PostgreSQL: 5432 MySQL: 3306 Oracle RDS: 1521 MSSQL Server: 1433 MariaDB: 3306 (same as MySQL) Aurora: 5432 (if PostgreSQL compatible) or 3306 (if MySQL compatible)

DNS

What is DNS

  • Domain Name system which transaltes the human friendly hostnames into machine ip addresses
  • www.google.com ->
  • DNS is backbone of internet
  • DNS uses hierarchical naming structure .com
    example.com
    www.example.com
    api.example.com

DNS Terminologies

  • Domain Registrar: Amazon Route 53, GoDaddy, ..
  • DNS Records: A, AAAA, CNAME, NS
  • Zone File: Contains DNS records
  • Name Server: resolves DNS queries (Authoritative or Non-Authoritative)
  • Top level Domain (TLD): .com, .in, .us, .ai, .gov, .org, ...
  • Second Level Domain (SLD): amazon.com, google.com
  • Sub-domain: www.example.com
  • Domain Name: api.www.example.com
  • Fully Qualified Domain Name (FQDN): http://api.www.example.com
   http://api.www.example.com. (last dot is Root )
                          TLD  
                  SLD........
             Sub-domain......
          Domain name........
protocol       
   ......FQDN................ Fully Qualified DOmain Name

How DNS Works?

5 pillars of well-architected framework

  • Cost
  • Performance
  • Security
  • reliability
  • Operationl Excellence

Different Concepts

RTO: Recovery Time Objective RPO: Recovery Point Objective

Boot Volume is a volume where operating system (Windows) stores its system files.

Throttling is the process of limiting the number of requests an authorized program can submit to a given operation in a given amount of time.

Throughput

Point in Time Recovery - point-in-time recovery point-in-time restore (PITR)

Blue/green deployment is a technique for releasing applications by shifting traffic between two identical environments running different versions of the application: "Blue" is the currently running version and "green" the new version. This type of deployment allows you to test features in the green environment without impacting the currently running version of your application. When you’re satisfied that the green version is working properly, you can gradually reroute the traffic from the old blue environment to the new green environment. Blue/green deployments can mitigate common risks associated with deploying software, such as downtime and rollback capability.

IPsec (internet protocol security) is a protocol suite for securing IP communications by authenticating and encrypting each IP packet in a data stream.

Scalability

Types

  • Vertical scalability means increasing the size of the instance.
    • For example, your application runs on a t2.micro.
    • Scaling up that application vertically means running it on a larger instance such as t2.large.
    • Scaling down that application vertically means running it on a smaller instance such as t2.nano.
    • Scalability is very common for non-distributed systems, such as a database. There’s usually a limit to how much you can vertically scale (hardware limit).
    • Example can be the instance type was upgraded from t2.nano to u-12tb1.metal, this is a scale-up example of vertical scalability.
  • Horizontal Scalability means increasing the number of instances/systems for your application.
    • When you increase the number of instances, it's called scale-out, whereas if you decrease the number of instances, it's called scale-in.
    • Scale-up is used in conjunction with vertical scaling and not with horizontal scaling.

Availability

  • High availability means running your application/system in at least 2 data centers (== Availability Zones).
  • The goal of high availability is to survive a data center loss. An example of High Availability is when you run instances for the same application across multi AZ.

AWS SDK

  • If you dont specify or configure a default region, then 'us-east-1' will be chosen by default

S3

Unicast vs Anycast IPs

  • Commerce tool
  • Wealth management
  • SF -> Stripe

NAS: Network Attach Storage (File System) SMB: Server Message Block (SMB) protocol iSCI: NFS file server ACL

OAI Origin access Identity Different gateways volume, Direct COnnect (DX)

Capex vs Opex

reconnaisance for pen testing recon.cloud whois

RTO Recovery Time Objective: Maximum acceptable downtime RPO Recovery Point Objective: MAximum acceptable period of data loss

RCU: Read Capacity units WCU: Write Capacity units

Caching strategies: Lazy loading (Cache Aside):

  • Cache Hit: Data found, Value from cache is used
  • Cache Miss: Data is not found, data is retrieved from db and added to cache Write through:
  • Cache is in sync with backend (Cache and database updated at same time)

Sporadic access

Throughput Throttling

Availability Resilience

Reliability