CAPACITY NOTES
Recalibrate your capacity plan after the first month
Planning math is a guess until production grades it. Compare planned and actual requests, peak rate, 429s and storage after a month, then adjust.
A capacity plan is a forecast, and production grades it within a month. Pull four actuals from your logs: requests per day, peak requests per second, the 429 share and storage growth. Compare them against the plan, then adjust the interval or the plan once, with evidence.
Start with the request count
The planning formula is one line: boards divided by interval, times active seconds, as the capacity planning guide sets out. After a month, your counter tells you what the formula could not: retries after 5xx and timeouts, the resynchronizations you actually needed, and how much busier the boards were than the slate you assumed.
If the actual runs more than about a fifth above planned, find the leak before touching the plan. A retry storm, a poller restarted every night by a deploy job, or a forgotten second environment each shows up as volume with no product value.
Grade the peak, not the average
The average request rate hides the only number the ceiling cares about: the busiest second. Your monitoring already records the request rate at peak, and the rate limits guide sets the rule: steady state under roughly 70 percent of the ceiling, with 429s above 1 percent of requests as the alarm.
A month inside those bounds means the plan fits. Repeated peaks past them, even with zero 429s so far, means you are one busy Saturday from triage.
Check storage against the arithmetic
The storage guide is explicit that its retention figures are an illustration, to be replaced by your own counts after a week of logging. A month in, you know the real rows per day. Compare against the retention plan: if the changes table grows faster than the estimate, the fix is almost always deduplication, not disk. Confirm that inserts happen only on price changes, then re-project the partition sizes.
Make one adjustment, with the evidence in front of you
The recalibration ends in exactly one of four moves. Actuals far under plan: poll faster or drop a tier at renewal. Actuals near the ceiling: slow the interval on the boards that need it least. Steady 429s: upgrade, because you measured, not because the wall annoyed you. Everything inside bounds: change nothing and write the numbers down as the new plan.
A plan you never revisit is a guess with a budget. A plan you revisit monthly is engineering.