# Deployment { #deployment }

Deploying a **FastAPI** application is relatively easy.

## What Does Deployment Mean { #what-does-deployment-mean }

To **deploy** an application means to perform the necessary steps to make it **available to the users**.

* **`200 - 299`** are for "Successful" responses. These are the ones you would use the most.
    * `200` is the default status code, which means everything was "OK".
    * Another example would be `201`, "Created". It is commonly used after creating a new record in the database.

# Lifespan Events { #lifespan-events }

You can define logic (code) that should be executed before the application **starts up**. This means that this code will be executed **once**, **before** the application **starts receiving requests**.

The same way, you can define logic (code) that should be executed when the application is **shutting down**. In this case, this code will be executed **once**, **after** having handled possibly **many requests**.

	CheckPrecondFn      CheckPreconditionFn // only set during GetObject/HeadObject/CopyObjectPart preconditional valuation
	EvalMetadataFn      EvalMetadataFn      // only set for retention settings, meant to be used only when updating metadata in-place.
	DeleteReplication   ReplicationState    // Represents internal replication state needed for Delete replication
	Transition          TransitionOptions

</div>

/// details | What that command means

* `echo "*"`: will "print" the text `*` in the terminal (the next part changes that a bit)
* `>`: anything printed to the terminal by the command to the left of `>` should not be printed but instead written to the file that goes to the right of `>`
* `.gitignore`: the name of the file where the text should be written

In all the docs there are examples compatible with each version of Python (when there's a difference).

For example "**Python 3.6+**" means it's compatible with Python 3.6 or above (including 3.7, 3.8, 3.9, 3.10, etc). And "**Python 3.9+**" means it's compatible with Python 3.9 or above (including 3.10, etc).

{* ../../docs_src/body_nested_models/tutorial009_py39.py hl[7] *}

/// tip

Keep in mind that JSON only supports `str` as keys.

But Pydantic has automatic data conversion.

This means that, even though your API clients can only send strings as keys, as long as those strings contain pure integers, Pydantic will convert them and validate them.

This is similar to the 200 HTTP status codes (from 200 to 299). Those "200" status codes mean that somehow there was a "success" in the request.

The status codes in the 400 range mean that there was an error from the client.

Remember all those **"404 Not Found"** errors (and jokes)?

## Use `HTTPException` { #use-httpexception }

   * has not added {@link AnnotatedType}. That means that we cannot implement that interface in
   * source code in a way that will compile on both Java and Android. If we include the {@code
   * getAnnotatedBounds()} method, then its return type means it won't compile on Android, while if
   * we don't include the method, then the compiler will complain that an abstract method is

Let's take this application as example:

{* ../../docs_src/query_params_str_validations/tutorial001_py310.py hl[7] *}

The query parameter `q` is of type `str | None`, that means that it's of type `str` but could also be `None`, and indeed, the default value is `None`, so FastAPI will know it's not required.

/// note