How should I practice Rate Limiter with Hourly and Daily Effort Quotas?

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Problem · Design

Rate Limiter with Hourly and Daily Effort Quotas

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ZscalerFULLTIMEPHONE SCREEN

Problem statement

Process a finite ordered sequence of requests. Request i belongs to userIds[i], costs efforts[i] units of effort, and arrives at timestamps[i], measured as a nonnegative Unix timestamp in seconds.

The same positive hourlyLimit and dailyLimit apply independently to every user. Define a request's fixed UTC hour bucket as floor(timestamps[i] / 3600) and its fixed UTC day bucket as floor(timestamps[i] / 86400).

Process requests in input order and apply these rules:

A request is accepted only when adding its effort keeps that user's accepted effort in both its hour bucket and its day bucket at or below the corresponding limits.
An accepted request adds its effort to both bucket totals.
A rejected request leaves all limiter state unchanged.
Different users maintain independent totals.

Return a boolean array in input order, where element i is true exactly when request i is accepted.

Function

applyRateLimits(userIds: String[], efforts: long[], timestamps: long[], hourlyLimit: long, dailyLimit: long) → boolean[]

Examples

Example 1

userIds = ["alice","alice","alice","alice","alice"]efforts = [4,6,1,5,1]timestamps = [0,60,120,3600,7200]hourlyLimit = 10dailyLimit = 15return = [true,true,false,true,false]

The first two requests fill Alice's first hour to 10. The third request is rejected and consumes no quota. The fourth request enters a new hour and brings the day total to 15; the fifth is rejected by the daily limit.

Example 2

userIds = ["alice","alice","bob","alice","alice"]efforts = [5,4,5,3,8]timestamps = [10,20,20,3601,86400]hourlyLimit = 8dailyLimit = 8return = [true,false,true,true,true]

Alice's second request would exceed both quotas and is rejected. Bob has independent totals. Alice can then use the remaining 3 units in a later hour, and the final request is accepted after the UTC day changes.

Example 3

userIds = ["u","u","u"]efforts = [7,4,3]timestamps = [100,100,100]hourlyLimit = 10dailyLimit = 10return = [true,false,true]

The rejected effort of 4 does not mutate state, so the final effort of 3 still fits exactly.

Constraints

userIds.length == efforts.length == timestamps.length.
Every userIds[i] is a non-empty string.
Every efforts[i], hourlyLimit, and dailyLimit is a positive signed 64-bit integer.
Every timestamps[i] is a nonnegative signed 64-bit integer, and timestamps is nondecreasing.
Hour and day buckets use fixed UTC boundaries derived from Unix time.