CMS

CMS with edge control, rate limiting, and feature management.

Requirements

Functional Requirements

• Evaluate flags
• Check limits
• Push updates

Non-functional Requirements

• Low-latency checks at edge
• High availability

High-Level Design

• Control plane → distribute policies
• Edge evaluate requests

Capacity & Sizing

• Checks/sec, policy size, propagation latency

Key Components

• Policy store, Edge cache, Evaluators

Architecture

Data Model

• policies (id PK, rules_json)
• counters (key PK, value, window)
• flags (flag PK, rules_json, variants)

APIs

• POST /api/flags { name, rules }
• GET /api/flags
• POST /api/ratelimits/check

Hot Path

1. Edge check → allow/deny

Caching & TTL

• Cache flags/policies at edge with short TTL and push invalidations

Scaling

• Sharded counters
• Eventually consistent policy caches
• Bloom filters for fast checks

Trade-offs

• Global consistency vs latency
• Push vs pull updates
• Precision vs memory in counters

Failure Modes & Mitigations

• Counter store outage → fail-open/closed
• Policy corruption → rollbacks
• Skew → per-key limits

Observability

• Limit hit rates
• Flag evaluation latency
• Edge error budgets