Tweaking WCF to build highly scalable async REST API

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Net;

namespace WcfAsyncRestApi
{
    /// <summary>
    /// Summary description for AsyncHandler
    /// </summary>
    public class AsyncHandler : IHttpAsyncHandler
    {

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }

        public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
        {
            HttpWebRequest request = WebRequest.Create(context.Request["url"]) as HttpWebRequest;
            return request.BeginGetResponse(cb, new MyState { Context = context, Request = request });
        }

        public void EndProcessRequest(IAsyncResult result)
        {
            var state = result.AsyncState as MyState;
            var webResponse = state.Request.EndGetResponse(result);
            var stream = webResponse.GetResponseStream();
            byte[] buffer = new byte[8000];
            int size = 0;

            state.Context.Response.AddHeader("Content-Type", "text/plain");
            do{
                size = stream.Read(buffer, 0, 8000);
                if (size > 0)
                    state.Context.Response.OutputStream.Write(buffer, 0, size);
            } while (size > 0);
            state.Context.Response.End();
        }


        public void ProcessRequest(HttpContext context)
        {
            throw new NotImplementedException();
        }
    }

    class MyState
    {
        public HttpContext Context;
        public HttpWebRequest Request;
    }
}