Dribbble Proxy: Upload Behaviour and Protocol Selection

On design-sharing platforms, traffic shows two different characters. While browsing the discovery feed, many small and medium-sized images come down in parallel; when uploading a piece of work, a large body flows upward over a single connection. A proxy does not affect these two directions in the same way.

In the download direction the most discussed topic is scope: which requests go through the proxy and which go directly. In the upload direction, the decisive factor is the behaviour of the transport layer; while large bodies are being sent, window size, retransmission and timeout settings directly affect the outcome.

The sections below first clarify the protocol decision with a criteria matrix, then open up the upload path layer by layer, and show how to set up regional view verification.

Which requests fall within proxy scope in the discovery feed?

When a discovery page opens, the browser first fetches the document skeleton, then the previews in the visible area, and then requests new ones as you scroll down. The practical meaning of this behaviour, called lazy loading, is this: a fixed set of requests does not form the moment the page opens; instead a request stream arises that grows in waves depending on how fast you scroll. The load on the proxy is therefore proportional not to the number of pages you open but to how far down you go on that page, and it keeps rising the longer you spend on the same page.

Some of these requests come from the main domain and some from separate asset servers; which hosts your rule covers is therefore decisive. Because the topic of scope definition and filter layers is covered in detail on the Behance proxy page, we do not repeat it here.

The detail that is the real subject of this page is connection reuse. Paying for a new TCP and TLS handshake every time for dozens of small requests noticeably lowers perceived speed; a client that uses persistent connections, on the other hand, sends requests back to back over the same tunnel and pays this setup cost once. When a proxy comes in between, the effect grows, because the handshake now happens on two separate legs: from client to proxy and from the proxy exit to the target. Check together whether your client establishes persistent connections and how long your provider keeps an idle connection open; for the mechanism, keep-alive and connection pooling article.

The third detail is the concurrency ceiling. Because the discovery feed works on infinite-scroll logic, the number of connections open simultaneously keeps rising throughout the session. The browser limits on its own how many parallel connections it will open to a single host; on the proxy side there is a separate ceiling defined by the provider, and the bottleneck forms at whichever of the two is lower. When you hit the provider's ceiling, the symptom is familiar: the first few previews arrive, the following ones queue up, and scrolling starts to stutter. To calculate the ceiling and set an upper limit based on your own usage, concurrent connection limit article.

Protocol matrix: tunnel or stream transport?

Five criteria are enough to decide: the ability to establish an encrypted tunnel, the ability to carry UDP, the ability to resolve the domain remotely, behaviour on large-body uploads, and ease of setup. The diagram below compares these criteria across three options.

HTTP proxy, CONNECT carries encrypted bytes without problems in the tunnel it establishes with it, and it is the easiest option to set up in a browser. It does not carry UDP; streams such as voice call or gaming traffic are therefore out of scope. In design platform use, this gap is not felt in practice.

SOCKS5 works independently of the protocol, UDP ASSOCIATE can also open a channel for UDP streams with its command, and offers the option of having the domain resolved on the proxy side. For details, see the articles on SOCKS5 UDP support and How a SOCKS5 proxy works .

The third row is a direct connection, given as a reference. With no intermediary at all, most of the criteria take the highest value; the only exception is that there is no option to choose your exit point. If you are undecided about protocol selection, the protocol selection guide summarises the decision tree.

The point to note when looking at the matrix is that the weight of the criteria changes with the job. If you will only work in the browser, the "UDP stream" column is meaningless for you and ease of setup comes to the fore. If you will also use the same access details in a design tool's sync client, the table flips: flexibility becomes more valuable than setup taking a few minutes longer.

The remote DNS column, meanwhile, is decisive on the privacy side. A client that resolves the domain locally tells its resolver which host it is going to, even if the connection itself goes through the proxy. Where this behaviour is configured varies from client to client; where DNS is resolved in SOCKS5 the article compares the options.

The data path layer by layer while uploading a piece of work

Uploading is not the mirror image of downloading. When sending a large image, the client streams data for a long time within a single request body. Meanwhile the topmost application layer produces multipart form data, the TLS layer below it splits this into encrypted records, the proxy layer carries it as a single TCP stream, and at the bottom the transport layer determines the speed of the stream.

When something goes wrong, the first place to look is most often the bottom layer. On a long-distance connection, window size and the response to packet loss affect upload speed more than any setting in the upper layers. For that reason, choosing a geographically closer exit for sessions in which you will upload makes a noticeable difference.

The second common problem is timeouts. Some proxy configurations close an idle connection after a certain period; hitting this limit while waiting for a response during a large upload appears as the file being cut off halfway. Check your provider's idle timeout and your client's timeout setting together.

The third is two layers running at once. With both a VPN and a proxy active, the upload path is wrapped twice; speed drops and it becomes impossible to tell which layer is causing the problem. During diagnosis, disable the layers one at a time.

A simple preparation before uploading also helps a great deal: check the file's size and format before sending it. A cover image stored losslessly for no reason can be several times the size of a compressed version that preserves the same visual quality. This directly affects both your quota and your upload time, and no setting on the proxy side can compensate for it.