Javalin Java

import io.javalin.Javalin;
import java.util.Base64;

public class Pixel {

    private static final byte[] GIF = Base64.getDecoder().decode("R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==");

    public static void main(String[] args) {
        Javalin.create(config -> {
            config.routes.get("/pixel.gif", ctx -> {
                ctx.contentType("image/gif");
                ctx.header("Cache-Control", "no-store");
                ctx.result(GIF);
            });
        }).start(8080);
    }
}