Set the concurrency that maximises throughput.

Throughput rises with concurrency, peaks at a knee, then collapses as contention dominates. More workers past the knee make the system slower, not faster.

Practice — no rating pressure. Get as close to the optimum as you can; each play teaches the pattern.

Throughput

28/s

11 workers

concurrency 1 → 21 (tap a bar or use the stepper)

Concurrency

Backpressure — practice the decision, scored against the optimum

What does the Backpressure puzzle teach?

Past the concurrency knee, adding workers reduces throughput — contention collapses the system.

Why do interviews ask about this?

Backpressure / queue control is the resilience interview — shed or buffer to keep tail latency bounded under overload.

How is it scored?

The engine computes the provably-optimal answer for the exact instance you played (dynamic programming, shortest-path, or exhaustive search — never a heuristic) and scores your attempt as a percentage of it. No login needed to see your score.

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Practice0:00

Backpressure · D4

Set the concurrency that maximises throughput.

Throughput rises with concurrency, peaks at a knee, then collapses as contention dominates. More workers past the knee make the system slower, not faster.

Practice — no rating pressure. Get as close to the optimum as you can; each play teaches the pattern.

Throughput

28/s

11 workers

concurrency 1 → 21 (tap a bar or use the stepper)

Concurrency