This includes, for example:

* Email notifications sent after performing an action:
    * As connecting to an email server and sending an email tends to be "slow" (several seconds), you can return the response right away and send the email notification in the background.
* Processing data:

    bytes: lambda o: o.decode(),
    Color: str,
    datetime.date: isoformat,
    datetime.datetime: isoformat,
    datetime.time: isoformat,
    datetime.timedelta: lambda td: td.total_seconds(),
    Decimal: decimal_encoder,
    Enum: lambda o: o.value,
    frozenset: list,
    deque: list,
    GeneratorType: list,
    IPv4Address: str,
    IPv4Interface: str,
    IPv4Network: str,

    app = FastAPI(generate_unique_id_function=broken_operation_id)

    @app.post("/")
    def post_root(item1: Item):
        return item1  # pragma: nocover

    @app.post("/second")
    def post_second(item1: Item):
        return item1  # pragma: nocover

    @app.post("/third")
    def post_third(item1: Item):
        return item1  # pragma: nocover

    client = TestClient(app)

Downloading and installing the package dependencies **could take minutes**, but using the **cache** would **take seconds** at most.

And as you would be building the container image again and again during development to check that your code changes are working, there's a lot of accumulated time this would save.