QPS Estimator

Convert DAU and per-user request volume into average QPS, peak QPS, and a capacity target with headroom.

QPS Estimator

Convert product traffic (DAU, actions/day, peakiness) into average and peak queries per second with capacity headroom.

Daily active users (DAU) Requests / user / day Peak factor vs avg e.g. 3–10× Read:write ratio reads per write Capacity headroom % Optional: known daily requests overrides DAU×RPU if > 0

Back-of-envelope for system design. Real peaks follow diurnal curves, launches, and cache hit rates — calibrate with metrics as soon as you have them.

Back-Of-Envelope Formula

Average QPS ≈ (DAU × requests_per_user_per_day) ÷ 86,400
Peak QPS ≈ average × peak_factor (often 3–10× depending on the product)
Capacity target ≈ peak × (1 + headroom)

If you already know daily requests, enter that to override DAU × RPU.

Using The Split

The read/write ratio helps separate:

Cache and read-replica capacity
Primary write capacity / queue depth

Replace peak_factor with real p99 traffic from metrics as soon as you can — estimators get you into the right order of magnitude for interviews and early design docs.