系統設計

1type Input = {
2  dau: number; actionsPerUser: number; readShare: number; objectBytes: number;
3  retentionYears: number; peakFactor: number; serverQps: number; cacheShare: number;
4};
5 
6function estimate(i: Input) {
7  const requestsPerDay = i.dau * i.actionsPerUser;
8  const averageQps = requestsPerDay / 86_400;
9  const peakQps = averageQps * i.peakFactor;
10  const readQps = peakQps * i.readShare;
11  const writeQps = peakQps - readQps;
12  const writesPerDay = requestsPerDay * (1 - i.readShare);
13  const storagePerYear = writesPerDay * i.objectBytes * 365;
14  const storageTotal = storagePerYear * i.retentionYears;
15  const peakEgress = readQps * i.objectBytes;
16  const servers = Math.max(1, Math.ceil(peakQps / i.serverQps));
17  const cacheBytes = requestsPerDay * i.readShare * i.objectBytes * i.cacheShare;
18  return { requestsPerDay, averageQps, peakQps, readQps, writeQps, writesPerDay,
19           storagePerYear, storageTotal, peakEgress, servers, cacheBytes };
20}