Design a content moderation system

Design a content moderation system for a large-scale product where users can submit content (e.g., text posts, images, videos, comments, or messages).

Your design should cover:

• What is being moderated: user-generated content before/after publishing.
• Policy outcomes: allow, block, label, downrank, age-gate, or send to human review.
• Scale/latency goals: handle high QPS; some content needs near-real-time decisions.
• Abuse resistance: adversarial users trying to evade detection.
• Human-in-the-loop: reviewer tooling, queues, SLAs, and escalation.
• Auditing/appeals: traceability and user appeals.

Provide an end-to-end architecture and justify key trade-offs (precision/recall, latency vs. quality, cost, and reliability).