- Basic problem and fundamental requirements
- Generalize the design & ask questions about that
- Future Scope
- Entities
- attributes
- behavior
- Relationships
- cardinality
- generalization (is-a)
- association (has-a)
- aggregation (no-ownership)
- composition (ownership)
- Clean Architecture - way/guideline for structuring and building your code
- Your directory structure / code structure should tell you exactly what you're building
- A good architecture allows you to delay the important decisions to as late as possible
Central thing of our problem statement
-
Entities, Relations b/w the entities & business logic
-
Are we knowledgeable enough to decide exactly what DB we should use?
-
Are we knowledgeable enough to decide exactly framework we should use?
- web
- http
- websockets
- commandline
- desktop application
- android app
- web
- Code the entities & relations & business logic (Domain)
- Usecases
- user logging in / logging out / updating profile
- ticket booking / cancel
- How to interact with the outside world?
- webserver
- command line interface
- Frameworks / libraries
- users can be of multiple types
- customer / employees / partnerships
- we don't want to put private/profile information in the user object
- have ONLY the authentication & autorization info in the User
- authentication: checking if the user is the person who they claim to be
- username (maybe your phone/email/string)
- password
- authorization: does the user have the required permissions/authority
- Role Based Authorization Control (RBAC)
- roles: instructor, mentor, admin
- privileges: add a new lecture / shift a lecture / message any mentee / view someones resume
- Role Based Authorization Control (RBAC)
- enums are good for static analysis and for code
- drawback: add / remove an option, you have to make a code change!
-
password must be b/w 8 .. 20 chars: varchar(20)
-
hashing & salting your password
-
Ashish - "Prashant"
-
Hash(Prashant) => shfsduhf => database
-
Hash(Prashant) => shfsduhf => does this match the value in my db?
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if Ashish and Aakash had the same password -> qwerty, password1, abcdefgh, zaqwsx
-
hash(qwerty) => kjdbfsf
-
hash(qwerty) => kjdbfsf
-
dictionary of commonly used password -> hash => rainbow table attack
-
Ashish => ;sdf;sduf
-
Aakash => poqjojesf
-
hash(password+salt)
-
hash(qwerty;sdf;sduf) => wbf;ewbf;owe, ;sdf;sduf
-
hash(qwerypoqjojesf) => sdbf;sdkbf;n, poqjojesf
Encoding:
- Representing information in some or another manner
- Image -> jpeg, png, gif, svg, bmp, raw --------lossy----------- --lossless--
- Audio -> mp3, wav, au3, wmv, aac, mp4
- Text -> base64, ASCII, utf-8, unicode
- Numbers -> hex, binary
Encryption:
- Making the information garbage for everyone except the authorized/intended reader
- If you don't have the "key" -> you can't make sense of the info
- If you do have the "key" -> you can easily reverse the encryption and get the plaintext back
Symmetric Key Cryptography: same key for locking an unlocking
- Ceaser / AES / DES Assymteric/Public Key Cryptogrpahy: 1 key to lock and a different key to unlock
- RSA
Hashing:
- Compressing the information in a lossy manner
- Making the information random
- a single bit change to the file contents will completely change the hash
- it IMPOSSIBLE to go back from the has to the plaintext
- MD5, BCrypt, SHA
- do NOT use MD5
UUID Long -> Auto-generated monotonic
Scaler.com Google.com / IBM / Oracle you architect some software today
Integer -> 32bit integers (4 bytes) -2^31 .. 2^31 - 1 (signed) 0 .. 2^32 - 1 (unsigned) 2^32 ~ 4 billion Number of people in the world? 7-8 billion Number of devices? Trillions
String -> not a good idea. Take up a lot of space, comparisons are slow rtl/ltr, ascii/unicode
Auto Base64 string - X ObjectId - X
// Uber
enum Color {
GREEN,
..
}
class Car {
String licensePlate;
String model;
String color; // arbitrary?
// turquoise blue
// brick red
// mauve
// hooloovoo
}
public enum Role {
ADMIN,
CUSTOMER,
PaidCustomer, // run the test, make the pull request // reviewed // merged // qa // staging server // AB-tested on 5% of production // public
PARTNERSHIP
}