"description": "Successful Response",
                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {

## Mounting a **FastAPI** application

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

### Top-level application

First, create the main, top-level, **FastAPI** application, and its *path operations*:

# 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**.

[19511] [INFO] Started server process [19511]
[19511] [INFO] Waiting for application startup.
[19511] [INFO] Application startup complete.
[19513] [INFO] Started server process [19513]
[19513] [INFO] Waiting for application startup.
[19513] [INFO] Application startup complete.
[19514] [INFO] Started server process [19514]
[19514] [INFO] Waiting for application startup.
[19514] [INFO] Application startup complete.
[19515] [INFO] Started server process [19515]

                            "description": "Successful Response",
                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {

The client will get a **500 Internal Server Error** for that request, but the application will continue working for the next requests instead of just crashing completely.

### Bigger Errors - Crashes

Nevertheless, there might be cases where we write some code that **crashes the entire application** making Uvicorn and Python crash. 💥

application/vnd.ms-powerpoint=powerpoint\n\
application/vnd.openxmlformats-officedocument.presentationml.presentation=powerpoint\n\
application/vnd.oasis.opendocument.text=odt\n\
application/vnd.oasis.opendocument.spreadsheet=ods\n\
application/vnd.oasis.opendocument.presentation=odp\n\
application/pdf=pdf\n\
application/x-fictionbook+xml=fb2\n\
application/e-pub+zip=epub\n\
application/x-ibooks+zip=ibooks\n\

[19511] [INFO] Started server process [19511]
[19511] [INFO] Waiting for application startup.
[19511] [INFO] Application startup complete.
[19513] [INFO] Started server process [19513]
[19513] [INFO] Waiting for application startup.
[19513] [INFO] Application startup complete.
[19514] [INFO] Started server process [19514]
[19514] [INFO] Waiting for application startup.
[19514] [INFO] Application startup complete.
[19515] [INFO] Started server process [19515]

                            "description": "Successful Response",
                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {

ff"},{"key":"frequency","value":"24h"}]},"compression":{"_":[{"key":"enable","value":"off"},{"key":"allow_encryption","value":"off"},{"key":"extensions","value":".txt,.log,.csv,.json,.tar,.xml,.bin"},{"key":"mime_types","value":"text/*,application/json,application/xml,binary/octet-stream"}]},"crawler":{"_":null},"credentials":{"_":null},"drive":{"_":[{"key":"max_timeout","value":""}]},"etcd":{"_":[{"key":"endpoints","value":""},{"key":"path_prefix","value":""},{"key":"coredns_path","value":"/sky...