How do you manage sessions and persist data?

1 What are sessions and why do you need them?

Sessions are a way of maintaining a stateful connection between the client and the server, even when the HTTP protocol is stateless. Sessions allow you to identify and track users across multiple requests, and store information about their preferences, actions, and permissions. You need sessions to implement features such as login, logout, shopping cart, and access control in your web applications.

2 How do you create and store sessions?

There are two main ways of creating and storing sessions: using cookies or using tokens. Cookies are small pieces of data that are sent from the server to the client, and stored in the browser. Cookies can store session IDs, user IDs, or other data that can be used to identify and authenticate users. Tokens are similar to cookies, but they are generated and stored on the client-side, usually using JavaScript. Tokens can contain encrypted or signed data that can be verified by the server without storing them in a database.

3 What are the pros and cons of cookies and tokens?

Cookies and tokens have different advantages and disadvantages, depending on your use case and security requirements. Cookies are easy to implement and compatible with most browsers and servers, but can be vulnerable to XSS and CSRF attacks, as well as size and number limitations that can affect performance and bandwidth. Tokens are more secure and flexible than cookies, but require more logic and storage on the client-side, along with expiration and revocation issues that can affect user experience. It is important to consider the pros and cons of each option when deciding which one is best for your needs.

4 How do you persist data on the client-side?

Persisting data on the client-side involves storing data in the browser, so that it can be accessed and modified even when the server is offline or unavailable. There are several ways to do this, such as LocalStorage, which is a key-value storage that can store up to 5 MB of data per domain and persists across browser sessions and tabs. SessionStorage is similar, but only persists within a browser session or tab. IndexedDB is a database that can store large amounts of structured or unstructured data with support for transactions, indexes, and queries. Web SQL is another database that can store up to 50 MB of data per domain and supports SQL queries and transactions. Finally, the Cache API enables offline access to web resources by storing network requests and responses.

5 How do you persist data on the server-side?

Persisting data on the server-side requires storing it in a database or a file system, so that it can be accessed and modified by the server or the application, regardless of the client's state or connection. There are various options for this, such as relational databases like MySQL, PostgreSQL, Oracle, etc., NoSQL databases such as MongoDB, Neo4j, Redis, etc., and file systems like local file systems or cloud storage services. These databases and systems use different query languages or APIs to manipulate and query data.

6 How do you choose the best method for your application?

When determining the best method for managing sessions and persisting data, you should consider factors such as the type and amount of data to store and access, security and privacy of users, performance and scalability of your application, compatibility and availability of your browser and server, as well as complexity and cost of development and maintenance. Evaluate these factors and compare the pros and cons of each method to decide which one is most suitable for your application. Additionally, it is important to test and monitor your application regularly to guarantee its functionality and security.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?