Deno のビルトイン key-value データベース Deno KV が登場

import { serve } from "https://deno.land/std@0.185.0/http/server.ts";

// Deno KV をオープン
const kv = await Deno.openKv();

// 事前にいくつかデータを登録
await kv.set(["books", "978-1-09-123456-2"], { title: "The Great Gatsby", author: "F. Scott Fitzgerald" });
await kv.set(["books", "978-1-09-123456-3"], { title: "The Grapes of Wrath", author: "John Steinbeck" });
await kv.set(["books", "978-1-09-123456-4"], { title: "Nineteen Eighty-Four", author: "George Orwell" }); 

// リクエストパスの定義
const BOOKS = new URLPattern({ pathname: "/books" });
const BOOKS_ISBN = new URLPattern({ pathname: "/books/:isbn" });

// ハンドラーの定義
async function handler(req: Request): Promise<Response> {
  const matchIsbn = BOOKS_ISBN.exec(req.url);
  const matchBooks = BOOKS.exec(req.url);

  if (matchIsbn) {
    const isbn = matchIsbn.pathname.groups.isbn;
    if (req.method === "GET") {
      // キーで取得する
      const res = await kv.get(["books", isbn]);  // ["books", isbn] がキー
      if (res.value) {
        return new Response(JSON.stringify(res.value), { status: 200 });
      }
      return new Response("Not found", { status: 404 });
    } else if (req.method === "DELETE") {
      // キーで削除
      await kv.delete(["books", isbn]); // キーが存在しない場合は no-op
      return new Response("OK", { status: 200 });
    }
  } else if (matchBooks) {
    if (req.method === "GET") {
      // 最大100件のリストを返却
      const iter = await kv.list({ prefix: ["books"] }, { limit: 100 });
      const books = [];
      for await (const res of iter) {
        books.push(res.value);
      }
      return new Response(JSON.stringify(books), { status: 200 });
    } else if (req.method === "POST") {
      // 入力データを登録
      const body = await req.json();
      const res = await kv.set(["books", body.isbn], { title: body.title, author: body.author });
      return new Response(res.versionstamp, { status: 201 }); // versionstamp を返却
    }
  }

  return new Response("Bad Request", { status: 400 });
}

serve(handler);

deno run --unstable --allow-net --watch mod.ts

# リストで取得
$ curl localhost:8000/books | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   177  100   177    0     0  26347      0 --:--:-- --:--:-- --:--:-- 88500
[
  {
    "title": "The Great Gatsby",
    "author": "F. Scott Fitzgerald"
  },
  {
    "title": "The Grapes of Wrath",
    "author": "John Steinbeck"
  },
  {
    "title": "Nineteen Eighty-Four",
    "author": "George Orwell"
  }
]

# キーで取得
$ curl localhost:8000/books/978-1-09-123456-2 | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    59  100    59    0     0   7439      0 --:--:-- --:--:-- --:--:-- 59000
{
  "title": "The Great Gatsby",
  "author": "F. Scott Fitzgerald"
}

# 登録
$ curl -X POST -H "Content-Type: application/json" localhost:8000/books -d '{"isbn":"978-1-09-123456-5","title":"hoge", "author":"mh"}'
00000000000001cd0000

# 削除
$ curl -X DELETE localhost:8000/books/978-1-09-123456-5                               
OK