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fix(backend): rate limiter admits the Nth request itself (off-by-one) - #2033
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masyarakatai wants to merge 1 commit into
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masyarakatai wants to merge 1 commit into
masyarakatai wants to merge 1 commit into
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The counter script increments before returning, so the maxRequests-th request comes back with currentCount === maxRequests. '<' rejected it even though it was still inside the window; '<=' fixes the off-by-one described in LabsCrypt#2027. Tests updated to pin the window boundary: the Nth request is admitted, the N+1-th is blocked, and a concurrent burst admits exactly maxRequests.
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Closes #2027.
Root cause:
INCR_AND_EXPIRE_SCRIPTincrements before returningcurrentCount, so whenmaxRequestsis 5, the 5th request already readscurrentCount: 5— and5 < 5rejected it. Every limiter oncheckRateLimittherefore allowedmaxRequests - 1per window.Fix: one operator —
currentCount <= config.maxRequestsinbackend/src/services/rateLimitService.ts(checkRateLimit), with a short comment explaining why<=is the honest boundary for this script.Tests (updated to pin the boundary the issue describes):
[5, ...] → not allowed, and the concurrent test expecting 4 allowed). Now:currentCount === maxRequestsis admitted withremaining: 0, and one past the limit (6) is blocked.Verification: service suite 9/9, middleware suite 10/10,
typecheckclean, lint clean of errors (39 pre-existing warnings untouched).