Slow download speeds for small files #1088

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1. dazzling-no-more commented on May 12, 2026

   

   dazzling-no-more

   on May 12, 2026

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   What mode are you on? Can you share the logs?
2. letmeinbruh13 commented on May 12, 2026

   

   letmeinbruh13

   on May 12, 2026

   Last edited by letmeinbruh13

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   What mode are you on? Can you share the logs?

   @dazzling-no-more I'm using full tunnel mode.

   Extra note: Using the download speed boost option in unofficial Telegram clients improves the download speed for both small and large files. However, there's still a difference between the download speed of small and large files.

   Logs attached:

   • 1mb.txt — log for 1 MB worth of video from a 6 MB video in Telegram (download speed boost was on, speed ~50 KB/s)
   • 13.9mb.txt — log for a 13.9 MB video in Telegram (download speed boost was on, speed ~300-600 KB/s)

   One more note:

   I believe this behavior may not be universal across all apps/websites. For example:
   • Downloading 6 MB from Cloudflare's speedtest — speed was good
   • Downloading from Instagram — the slow-down behavior can be observed. in fact, all videos with all sizes load slowly. but in the web version the behavior is different and needs further checks
   edit: the web version of Instagram is fine. i guess the web version of telegram should be fine too.

   👍React with 👍1Reacted by dazzling-no-more
3. therealaleph commented on May 12, 2026

   

   therealaleph

   on May 12, 2026

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   Reviewed via Anthropic Claude.

   @letmeinbruh13 — "small files slow, large files fast" on Full mode is consistent with how the batch coalesce works:

   • Large files (>10 MB): range-parallel path. mhrv-rs fires up to 8 parallel 256 KiB chunk requests. Each Apps Script call brings back ~256 KiB. Throughput compounds — actual speed is bounded by your weakest connection segment (Apps Script edge → your ISP).
   • Small files (<10 MB): single-request path. One Apps Script round-trip for the entire file. Latency dominates throughput here — even at 50-80 KB/s, a 5 MB file is ~60-100 seconds.

   This isn't a bug; it's the structural cost of doing each small file in one round-trip. The fix is request batching across multiple small files, which is what Code.gs's spreadsheet cache () addresses for repeat assets — once you've seen the same URL once, subsequent fetches come from the spreadsheet cache instantly. v1.9.23 (just shipped) also has the large-file streaming fix from #1085 that improves throughput for the >40 MiB range.

   Tuning that helps small-file throughput today:

   • parallel_relay: 2 (or higher, up to your script_id count): fan out small requests across multiple deployments for first-byte latency improvement
   • coalesce_max_ms: 2000: pack more concurrent small-file requests into one batch
   • More script_id entries from different Google accounts: round-robin reduces per-deployment quota pressure

   For HTTP API calls (REST endpoints returning JSON, etc.) which are intrinsically small-file requests, 50-80 KB/s in Full mode is roughly what Apps Script's per-request RTT allows. Switching to apps_script mode (no tunnel-node middleman) usually helps for those — one less layer.

   Closing — expected behavior. If you're seeing speeds much worse than 50-80 KB/s for small files (e.g. sub-10 KB/s) that's separate and worth a new issue with timing data.

   ❤️React with ❤️1Reacted by letmeinbruh13
4. therealaleph

   closed this as completedon May 12, 2026
5. letmeinbruh13 commented on May 12, 2026

   

   letmeinbruh13

   on May 12, 2026

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   • Small files (<10 MB): single-request path. One Apps Script round-trip for the entire file. Latency dominates throughput here — even at 50-80 KB/s, a 5 MB file is ~60-100 seconds.

   @therealaleph I understand the need for lower latency with smaller files, but some types of files fall into a gray area. For example, most Instagram and Telegram videos are well below 10 MB, and to watch a 30-second video, sometimes we have to wait 140 seconds for it to load completely. Isn't there a way to make certain file formats or specific services like Instagram/Telegram use the batch-request path you mentioned to make watching videos a smoother experience in full tunnel mode?
6. therealaleph

   added 2 commits that reference this issue on May 13, 2026

   fix(tunnel): batch header read honors request_timeout_secs (#1088, #1108

   ...

   4d135a4

   chore(release): v1.9.24 — fix timeout cascade + Cloud Run docker build (

   ...

   1c9e73e