As software developers, we have a limited 'performance' coins. It's up to us to decide where to spend it, either on 'security' or 'user experience.' Make your choice wisely.

Why do we need a refresh token?

We need a refresh token to maintain user sessions and extend their access to a resource without requiring frequent authentication. In other words, to improve the user experience.

Imagine you're using a mobile app for a social media platform. You log in and start scrolling through your feed. Your session is active, and you don't need to log in again every time you open the app. This seamless experience is made possible with the help of refresh tokens.

Here's how it works:

1. Access Tokens: When you initially log in, you receive an access token. This token allows you to access your data (e.g., posts, and messages) on the platform.

2. Expiry: Access tokens have a relatively short lifespan, usually just a few minutes. They are time-limited keys that grant you access.

3. Refresh Tokens: To avoid forcing you to log in frequently, the app also provides you with a refresh token. This token is long-lasting and can be used to request a new access token when the old one expires.

4. Seamless User Experience: When your access token expires (e.g., after 15 minutes), the app quietly uses your refresh token to get a new access token without requiring you to log in again. This keeps your session active, and you can continue using the app without interruptions.

So, refresh tokens are a crucial part of maintaining a smooth and secure user experience. They keep you logged in without needing to constantly re-enter your credentials.

What is the nature of a refresh token?

A refresh token can be constructed or opaque.

Constructed Refresh Token(Using JWT)

A constructed refresh token as a JSON Web Token (JWT) is a refresh token that is designed using the JWT format. In this context, a JWT is a self-contained data structure that consists of three parts: a header, a payload, and a signature.

Advantages of JWT Refresh Tokens:

• Statelessness: Self-contained, no need for server-side session storage.

• Consistency: Uniform token format simplifies application code.

Disadvantages of JWT Refresh Tokens:

• Security Risks: Sensitive information exposure if compromised.

• Revocation Challenges: Complex revocation mechanisms may be needed.

• Increased Complexity: Requires careful management and extra security measures.

Opaque refresh token

An opaque refresh token is a type of token used in authentication and authorization systems that is random and non-human-readable, making it difficult to decipher its content. It contrasts with transparent tokens like JSON Web Tokens (JWTs) that contain easily readable information.

Advantages of Opaque Refresh Tokens:

• Enhanced Security: Opaque tokens conceal sensitive user and session data, reducing exposure risk.

• Reduced Information Leakage: Minimal risk of data leakage in case of token compromise.

• Flexibility and Simplicity: Offers flexibility for server-side session management, simplifying handling.

• Ease of Revocation: Revocation is straightforward, enhancing security control.

Disadvantages of Opaque Refresh Tokens:

• Server-Side Storage: Requires additional server-side data storage, increasing complexity.

• Additional Round-Trips: Token validation may necessitate extra server round-trips, introducing slight delays.

• Token Rotation Complexity: Handling token rotation can be more intricate compared to self-contained tokens like JWTs.

So based on the above information, as a software developer you need to decide where you want to spend your "performance coins".

With a refresh token as a JWT, you can't revoke it, but the user experience will be seamless.

With an opaque refresh token, you gain security. You will be able to revoke it but it requires additional database or cache lookup which cost performance.

Choose wisely!