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head-of-line blocking
One slow item at the front of a single queue stalls everything behind it. Split the queue or the connection.
What is head-of-line blocking?
Head-of-line blocking is when ordered processing on one pipe makes a delay at the front block unrelated work behind it. HTTP/1.1 does it per connection. A single worker does it per topic partition. HTTP/2 fixed it for requests and can still suffer it on one lost packet.
Why does head-of-line blocking matter when vibe coding?
Models put every job type on one ordered queue. A slow report blocks password resets. Name separate lanes.
How do you do head-of-line blocking?
Separate queues for latency-sensitive work. Do not require global order if the tasks are independent. More HTTP connections or HTTP/2 for many small assets, with a cap.
How do you ask a model for head-of-line blocking?
Prevent head-of-line blocking for (fast work). Give it its own queue or connection. Do not process it behind (slow work) on one ordered lane. Do not require global order unless the tasks actually depend on it.
What goes wrong with head-of-line blocking?
Ten connections per user to dodge blocking and melting the server. Cap concurrency. The browser will open them all.