},
                }
            ]
        }
    ) | IsDict(
        # TODO: remove when deprecating Pydantic v1
        {
            "detail": [
                {
                    "loc": ["body", 1],
                    "msg": "Expecting property name enclosed in double quotes: line 1 column 2 (char 1)",

                    },
                }
            ]
        }
    ) | IsDict(
        # TODO: remove when deprecating Pydantic v1
        {
            "detail": [
                {
                    "loc": ["body", 1],
                    "msg": "Expecting property name enclosed in double quotes: line 1 column 2 (char 1)",

But as TypeScript data is not preserved after compilation to JavaScript, it cannot rely on the types to define validation, serialization and documentation at the same time. Due to this and some design decisions, to get validation, serialization and automatic schema generation, it's needed to add decorators in many places. So, it becomes quite verbose.

* HAProxy

## Let's Encrypt

Before Let's Encrypt, these **HTTPS certificates** were sold by trusted third parties.

The process to acquire one of these certificates used to be cumbersome, require quite some paperwork and the certificates were quite expensive.

But then **<a href="https://letsencrypt.org/" class="external-link" target="_blank">Let's Encrypt</a>** was created.

## Recap

With what you have seen up to now, you can set up a secure **FastAPI** application using standards like OAuth2 and JWT.

In almost any framework handling the security becomes a rather complex subject quite quickly.

Many packages that simplify it a lot have to make many compromises with the data model, database, and available features. And some of these packages that simplify things too much actually have security flaws underneath.

Here's where you import and use the class `FastAPI`.

This will be the main file in your application that ties everything together.

And as most of your logic will now live in its own specific module, the main file will be quite simple.

### Import `FastAPI`

You import and create a `FastAPI` class as normally.

* ✏ Fix typos in Deployment Guide. PR [#3975](https://github.com/tiangolo/fastapi/pull/3975) by [@ghandic](https://github.com/ghandic).
* 📝 Update docs with pip install calls when using extras with brackets, use quotes for compatibility with Zsh. PR [#3131](https://github.com/tiangolo/fastapi/pull/3131) by [@tomwei7](https://github.com/tomwei7).

**Concurrency** and **parallelism** both relate to "different things happening more or less at the same time".

But the details between *concurrency* and *parallelism* are quite different.

To see the difference, imagine the following story about burgers:

### Concurrent Burgers

But if you need to change some of the defaults, support more than one predefined database, work with an async framework (like FastAPI), etc, you will need to add quite some complex extra code to override those defaults.

Nevertheless, it's possible to do it, and here you'll see exactly what code you have to add to be able to use Peewee with FastAPI.

!!! note "Technical Details"

The same models are shared among requests, so, it's not one model per request, or one per user or something similar.

Let's imagine that loading the model can **take quite some time**, because it has to read a lot of **data from disk**. So you don't want to do it for every request.