Pastebin System Design

Problem

Level: hld
Difficulty: easy
Estimated time: 20 min

create successful requests ≥ 9.5 rps

Choose who can see a paste: anyone (public), anyone with the link (unlisted), or only its signed-in owner (private).functional · not simulated

Choose when a paste expires, from 10 minutes to never; a year by default. An expired paste is gone everywhere within a minute, cached copies included.functional · not simulated

Burn after reading: the first view shows the paste, then it is gone for everyone. Optionally protect a paste with a password.functional · not simulated

view p99 latency < 200 ms

view-direct p99 latency < 200 ms

create p99 latency < 500 ms

throughput ≥ 520 rps

Viewing keeps working while one database server or one app server is down; creating may pause for a failover.functional · not simulated

Once its link is shown, a paste survives the loss of any one machine or disk, until it expires or is deleted.functional · not simulated

scrape refused over quota > 90%

Spam and stolen data are caught: limits on creating, a scan of every new paste, reports, and takedowns that also clear cached copies.functional · not simulated

Request pathshover to trace

Scenarios

Walkthroughs

Estimates

new pastes a day → requests, storage and what is kept

New pastes a day300,000

Views per paste50

Peak ÷ average3

Average size (KB)10

Compression3

Share kept a year (the default)0.8

Share kept forever0.1

Years5

New pastes a second at peak: —
Views a second at peak: —
Text written a year: —
Pastes kept: —
Text kept: —
Database size: —
Expiries a second, after the first year: —

Results appear once the simulation starts.

p99 latency

—ms

error rate

—%

throughput

—rps

refused over quota

—rps

spent so far

—1 min = 1 mo

Live metrics, last 60 seconds
Metric	Now	Versus baseline	60 s low	60 s high
p99 latency	—	—	—	—
error rate	—	—	—	—
throughput	—	—	—	—
refused over quota	—	—	—	—

Loading the simulation…