Capacity planning
Before the servers run out
Capacity planning means having enough servers before players need them. Google's SRE book lists three steps it calls mandatory.
Three steps
From the SRE book:
- Organic forecastNormal growth, forecast "beyond the lead time required for acquiring capacity".
- Inorganic demandKnown events on top: a launch, a sale, a famous streamer.
- Load testsTurn raw capacity, like servers and disks, into how many players that serves.
Quick check
A famous streamer will play Shard Garden on Saturday. What kind of demand is that?
- Inorganic: a known event on top of normal growth
- Organic
- Not demand at all
Show the answer
Inorganic: a known event on top of normal growth
Organic demand is steady growth. A planned event is added on top of the forecast, as inorganic demand.
Lead time
Priya knows that some capacity takes time to get: a bigger quota from the cloud provider, a reserved server, a new region. If that takes two weeks, a forecast that only looks one week ahead is no use. The forecast must reach past the lead time.
Do the math
1Peak players now 8,0002Growth a month 25%3Players a server 1,000
How many race servers will next month's peak need?
- 10
- 8
- 9
Show the answer
10
8,000 plus 25% is 10,000 players. At 1,000 players a server, that is 10 servers, before any spare.
Where "1,000 a server" comes from
That number is not a guess. It came from a load test: robot players added until a race server's p95 start time broke its target. The forecast says how many players are coming; the load test says how many servers that means.
Spare room
A plan with exactly enough servers fails the moment one breaks at peak. N+1 means one spare: enough to carry the peak even with one server down.
Quick check
Next month's peak needs 10 race servers. With N+1, how many does Priya run?
- 11
- 10
- 20
Show the answer
11
N is the 10 the peak needs. Plus 1 spare is 11, so losing any one server still leaves 10.
Spare costs money
Every spare server costs money, every hour. The last lesson of this stage asks what the money buys.
Bolt says: Next: cloud costs.
Fact-checked 12 October 2026
- Google SRE book: Introduction (demand forecasting and capacity planning) sre.google