public static void rotate(int[] array, int distance, int fromIndex, int toIndex) {
    // There are several well-known algorithms for rotating part of an array (or, equivalently,
    // exchanging two blocks of memory). This classic text by Gries and Mills mentions several:
    // https://ecommons.cornell.edu/bitstream/handle/1813/6292/81-452.pdf.
    // (1) "Reversal", the one we have here.

Here's a little bit of that history.

## Alternatives { #alternatives }

I have been creating APIs with complex requirements for several years (Machine Learning, distributed systems, asynchronous jobs, NoSQL databases, etc), leading several teams of developers.

As part of that, I needed to investigate, test and use many alternatives.

The history of **FastAPI** is in great part the history of its predecessors.

## OAuth2 { #oauth2 }

OAuth2 is a specification that defines several ways to handle authentication and authorization.

It is quite an extensive specification and covers several complex use cases.

It includes ways to authenticate using a "third party".

    assertEquals(a, navigableMap.pollLastEntry());
    assertTrue(navigableMap.isEmpty());
  }

  @CollectionSize.Require(SEVERAL)
  public void testFirst() {
    assertEquals(a, navigableMap.firstEntry());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(SEVERAL)
  public void testPollFirst() {
    assertEquals(a, navigableMap.pollFirstEntry());

  public void testSingletonMapLast() {
    assertEquals(a.getKey(), navigableMap.lastKey());
  }

  @CollectionSize.Require(SEVERAL)
  public void testFirst() {
    assertEquals(a.getKey(), navigableMap.firstKey());
  }

  @CollectionSize.Require(SEVERAL)
  public void testLast() {
    assertEquals(c.getKey(), navigableMap.lastKey());
  }

  @CollectionSize.Require(absent = ZERO)

  public void testSingletonMapLast() {
    assertEquals(a.getKey(), navigableMap.lastKey());
  }

  @CollectionSize.Require(SEVERAL)
  public void testFirst() {
    assertEquals(a.getKey(), navigableMap.firstKey());
  }

  @CollectionSize.Require(SEVERAL)
  public void testLast() {
    assertEquals(c.getKey(), navigableMap.lastKey());
  }

  @CollectionSize.Require(absent = ZERO)

///

### Flask REST frameworks { #flask-rest-frameworks }

There are several Flask REST frameworks, but after investing the time and work into investigating them, I found that many are discontinued or abandoned, with several standing issues that made them unfit.

But when checking benchmarks and comparisons you should keep the following in mind.

## Benchmarks and speed { #benchmarks-and-speed }

When you check the benchmarks, it is common to see several tools of different types compared as equivalent.

Specifically, to see Uvicorn, Starlette and FastAPI compared together (among many other tools).

///

## Separating tests { #separating-tests }

In a real application, you probably would have your tests in a different file.

And your **FastAPI** application might also be composed of several files/modules, etc.

### **FastAPI** app file { #fastapi-app-file }

Let's say you have a file structure as described in [Bigger Applications](bigger-applications.md){.internal-link target=_blank}:

```
.
├── app

But there are several cases in which you might benefit from using `UploadFile`.

## File Parameters with `UploadFile` { #file-parameters-with-uploadfile }

Define a file parameter with a type of `UploadFile`:

{* ../../docs_src/request_files/tutorial001_an_py39.py hl[14] *}

Using `UploadFile` has several advantages over `bytes`: