* The item the client was trying to access doesn't exist.
* etc.

In these cases, you would normally return an **HTTP status code** in the range of **400** (from 400 to 499).

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.

  private val algorithmParameters: DerAdapter<Any?> =
    Adapters.usingTypeHint { typeHint ->
      when (typeHint) {
        // This type is pretty strange. The spec says that for certain algorithms we must encode null
        // when it is present, and for others we must omit it!
        // https://tools.ietf.org/html/rfc4055#section-2.1

        "price": 42.0,
        "tax": 3.2
    },
    "user": {
        "username": "dave",
        "full_name": "Dave Grohl"
    }
}
```

/// note

Notice that even though the `item` was declared the same way as before, it is now expected to be inside of the body with a key `item`.

///

# Separate OpenAPI Schemas for Input and Output or Not { #separate-openapi-schemas-for-input-and-output-or-not }

Since **Pydantic v2** was released, the generated OpenAPI is a bit more exact and **correct** than before. 😎

In fact, in some cases, it will even have **two JSON Schemas** in OpenAPI for the same Pydantic model, for input and output, depending on if they have **default values**.

Let's see how that works and how to change it if you need to do that.

```
http://127.0.0.1:8000/items/?skip=20
```

The parameter values in your function will be:

* `skip=20`: because you set it in the URL
* `limit=10`: because that was the default value

## Optional parameters { #optional-parameters }

The same way, you can declare optional query parameters, by setting their default to `None`:

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

For active-active replication, automatic failover occurs on `GET/HEAD` operations if object or object version requested qualifies for replication and is missing on one site, but present on the other. This allows the applications to take full advantage of two-way replication even before the two sites get fully synced.

# MinIO Grid

The MinIO Grid is a package that provides two-way communication between servers.
It uses a single two-way connection to send and receive messages between servers.

It includes built in muxing of concurrent requests as well as congestion handling for streams.

Requests can be "Single Payload" or "Streamed".

Use the MinIO Grid for:

* Small, frequent requests with low latency requirements.

<img src="/img/tutorial/body/image03.png">

You also get error checks for incorrect type operations:

<img src="/img/tutorial/body/image04.png">

This is not by chance, the whole framework was built around that design.

And it was thoroughly tested at the design phase, before any implementation, to ensure it would work with all the editors.

There were even some changes to Pydantic itself to support this.

   * {@link #peek()} methods on this instance; if it does, an {@code IllegalStateException} will
   * result.
   *
   * @return the next element if there was one. If {@code endOfData} was called during execution,
   *     the return value will be ignored.
   * @throws RuntimeException if any unrecoverable error happens. This exception will propagate

2. **Thoughtful, honest feedback.** We will consider every contribution on its merits, regardless of whether AI was used. We may not respond quickly—our review queue is long—but we will tell you clearly what works, what needs to change, and why.