HLD-110·Storage & Caching
Easy · 500 ptsTransactional Email Bounce & Suppression Store
Design a pre-send email suppression lookup service queried before every outbound message so hard-bounced or unsubscribed recipients are never emailed again.
Max p99
≤ 35 ms
Availability
≥ 99.5%
Budget
≤ $2,150
Functional Requirements
- FR-1GET /suppression/{email_hash} — Checks whether an address is suppressed prior to SMTP dispatch.
- FR-2POST /bounces — Records ISP hard-bounce and unsubscribe webhooks durably.
- FR-3DELETE /suppression/{email_hash} — Supports tenant retention TTL expiry, rule updates, or stream cleanup while keeping recent rollup caches fresh.
- FR-4Must remain online across a primary database crash during marketing campaign blasts.
Workload Profile
Baseline Checks15,000 Read RPS / 2,000 Bounce Write RPS
Campaign Blast Peak46,000 Read RPS / 6,000 Write RPS
Active Working Set12 GB hot suppression set & Bloom/cache tier
Traffic DistributionModerate skew across active recipient domains
Consistency Model
Eventual suppression propagation (< 5s) acceptable; recorded hard bounces must never be lost.
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