We are going to start from where we left in the previous chapter and increment it.

## About JWT

JWT means "JSON Web Tokens".

It's a standard to codify a JSON object in a long dense string without spaces. It looks like this:

```
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c
```

You probably wouldn't want to take your crush 😍 with you to do errands at the bank 🏦.

### Burger Conclusion

In this scenario of "fast food burgers with your crush", as there is a lot of waiting 🕙, it makes a lot more sense to have a concurrent system ⏸🔀⏯.

This is the case for most of the web applications.

Many, many users, but your server is waiting 🕙 for their not-so-good connection to send their requests.

"_Si vous cherchez à apprendre un **framework moderne** pour créer des APIs REST, regardez **FastAPI** [...] C'est rapide, facile à utiliser et à apprendre [...]_"

"_Nous sommes passés à **FastAPI** pour nos **APIs** [...] Je pense que vous l'aimerez [...]_"

}

// A StatefulSetSpec is the specification of a StatefulSet.
message StatefulSetSpec {
  // replicas is the desired number of replicas of the given Template.
  // These are replicas in the sense that they are instantiations of the
  // same Template, but individual replicas also have a consistent identity.
  // If unspecified, defaults to 1.
  // TODO: Consider a rename of this field.
  // +optional

And if there's any other style or consistency need, I'll ask directly for that, or I'll add commits on top with the needed changes.

### Check the code

* Check and read the code, see if it makes sense, **run it locally** and see if it actually solves the problem.

* Then **comment** saying that you did that, that's how I will know you really checked it.

!!! info

}

// A StatefulSetSpec is the specification of a StatefulSet.
message StatefulSetSpec {
  // replicas is the desired number of replicas of the given Template.
  // These are replicas in the sense that they are instantiations of the
  // same Template, but individual replicas also have a consistent identity.
  // If unspecified, defaults to 1.
  // TODO: Consider a rename of this field.
  // +optional

    ...Although if the whole application is just **crashing immediately** it probably doesn't make sense to keep restarting it forever. But in those cases, you will probably notice it during development, or at least right after deployment.

    So let's focus on the main cases, where it could crash entirely in some particular cases **in the future**, and it still makes sense to restart it.

* Keep commits discrete. Avoid including multiple unrelated changes in a single commit.
* Keep commits self-contained. Avoid spreading a single change across multiple commits. A single commit should make sense in isolation.

### Testing changes

After making changes, you can test your code in 2 ways:

1. Run tests.

Here are some examples of when that could make sense:

#### A Simple App

* **Machine Learning**: Normalmente exige muita multiplicação de matrizes e vetores. Pense numa grande folha de papel com números e multiplicando todos eles juntos e ao mesmo tempo.