Django Interview Preparation

Django Request Life Cycle  A web application or a website revolves around the request-response cycle and Django applications are no exception to this. But it is not just a two step process. Our Django applications needs to go through various stages to return the end user some result. To understand the Django framework better we must understand how the requests are initiated and the end result is served to the end user. When setting up a new Django project, one of the first things you’ll do is wire up your URLconfs and set up some views. But what’s actually happening under the hood here? How does Django route traffic to the view, and what part do middlewares play in this cycle? Layers of Django Application Request Middlewares URL Router(URL Dispatcher) Views Context Processors Template Renderers Response Middlewares Whenever a request comes in first it goes to the web server (Ngnix /Apache) . The the request goes to django's WSGI (Web Server Gateway Interface) / ASGI  (Asynchr...

OAuth(Open Authorization) and JWT(Json web token) are both standards for authorization and authentication. OAuth is suitable for delegating user authorization, accessing third-party applications, and session management.  OAuth allows third-party services such as Facebook and Google to use end-user account information without exposing the user’s account credentials to a third party. JWT is suitable for stateless applications, API authentication, and server-to-server authorization. A JWT contains a JSON object with information that needs to be shared. Additionally, each JWT is cryptographically signed, so that clients or malicious parties cannot modify JSON content When to Use JWT vs. OAuth: Use JWT When: 1. You're building a stateless authentication system, such as a RESTful API. 2. You want a lightweight and straightforward authentication mechanism. 3. You have full control over both the client and the server. 4. You don't need to delegate access to third-party applications. Us...

When optimizing a Django project for large write operations, especially when dealing with PostgreSQL, there are several strategies you can employ to reduce the time it takes to perform these operations: 1. Bulk Inserts In django, we create objects using create()  . Asynchronous version is acreate() .It's a  convenience method for creating an object and saving it all in one step.  and  These are same and equivalent. The create() method is used to create and save a single object in the database. Example: Instead of inserting one row at a time, consider using Django's bulk_create() method to insert multiple rows in a single query. This reduces the overhead of multiple database round trips. Example:  The bulk_create() method is used to create and save multiple objects in the database in a single query. It accepts a list of model instances and inserts them into the database in a single batch operation, which significantly reduces the overhead compared to individ...

Importance of JWT JWT (JSON Web Token) is a form of transmitting a JSON object as information between parties. Let's learn more about what JWTs are and how they work. JWTs are important for two main reasons: 1. Authorization 2. Information exchange JSON Web Token comprises 3 strings separated by “.” as follows where each part is encoded with base64url encoding : “eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJyb2xlIjp7ImlkIjoiNTlhZDFmZTI0MDVkNzk0YTFkYWQ2YmFkIiwiZGlzcGxheV9uYW1lIjoiQWRtaW4iLCJyb2xlX3R5cGUiOiJhZG1pbiJ9LCJpZCI6IlwiNTliYmJjODc0MDVkNzk0NjYwNGEzZjUyXCIiLCJlbWFpbCI6Imp5b3RpZ2F1dGFtMTA4QGdtYWlsLmNvbSJ9.oGA-goFi7ee6DdKn0Z4sctomaY6Ki0mfuJfxT4OK9WA” 1. Header 2. Payload 3. Signature Header: The header contains:      t ype: the specification that the token is a JWT      algorithm: the signing algorithm used to sign said token Algorithms that are used to sign include RSA, HMAC, or SHA256. The signatures for the tokens serve two purposes – integrity ...

  Django Password Django provides a flexible password storage system and uses PBKDF2 by default. Django saves the password as below. <algorithm>$<iterations>$<salt>$<hash> example of a Hashed password stored in database: pbkdf2_sha256$390000$LCm33kvO7rbjbZhwJA90Sf$xfuGOzl/MJyUxqWNhsNdSThaQUvn1EjEfxZ48HA8HF4= Those are the components used for storing a User’s password,separated by the dollar-sign character and consist of:  1. The hashing algorithm 2. The number of algorithm iterations (work factor) 3. The random salt 4. The resulting password hash.  Most password hashes include a salt along with their password hash in order to protect against rainbow table attacks. Example of Making Hashed password: Here’s a simplified overview of how Django handles password storage: 1. Password Creation or Change : # When someone creates a new account or decides to change their password, Django takes their chosen password and performs a process called hashing. Has...

  Database Indexing Database indexing is a technique used to optimize the performance of database queries by allowing the database management system (DBMS) to quickly locate and retrieve specific rows of data. Indexes are data structures that provide a faster way to look up records based on the values stored in one or more columns of a table. When you create an index on a table, the DBMS creates a separate data structure that maps the values in the indexed columns to the corresponding rows in the table. Default Type of Index is B-Tree Index ( The king of all indexes) বইতে কোন টপিক খুজতে গেলে আমরা টেবিল অফ কনটেন্ট থেকে দেখি এই টপিক কত নম্বর পেজে আছে।যাতে করে আমাদের পুরো বই খুজতে না হয়। ডেটাবেজ ইনডেক্সিং ও তেমনই একটা ইফিসিয়েন্ট টেকনিক।ডেটাবেজে কোন ডেটাকে দ্রুত খুজে বের করার জন্য ইনডেক্সিং করা লাগে।যদি এমন হয় একটা কুয়েরি বার বার এক্সিকিউট করতে হচ্ছে এবং একটা কলাম থেকে ভ্যালু বার বার খুজতে হচ্ছে তখন আমরা সেই কলামে ইনডেক্সিং করতে পারি।এর মাধ্যমে কোন ডেটা দ্রুত রিট্রাইভ করা যায়।কিন্তু ই...