← Lessons

quiz vs the machine

Gold1460

System Design

Content Moderation In Feeds

Filtering harmful and policy violating content before and after it enters feeds.

4 min read · core · beat Gold to climb

Keeping the feed safe

A feed cannot just rank for engagement. It must keep harmful and policy violating content out, spam, abuse, and banned material. Moderation is a stage the pipeline cannot skip.

When moderation runs

  • At ingestion, when a post is created, automated classifiers scan text, images, and video for clear violations and can block or hold the post before fan out.
  • At serving, the feed pipeline filters out content later flagged or from blocked authors, so removed items vanish even after they were fanned out.

Running checks at both points catches violations that slip past the first gate.

How decisions are made

  • Automated models score content for categories like spam and abuse, acting on high confidence and queuing the rest.
  • A human review queue handles uncertain or appealed cases, and their labels train the models.
  • User reports feed signals that re evaluate already published content.

The tradeoffs

Moderation balances speed, accuracy, and scale. Blocking too aggressively removes good content, blocking too little lets harm through. Most systems combine fast automated filters with slower human judgment.

Key idea

Feed moderation filters harmful content at ingestion and again at serving, combining automated classifiers, human review, and user reports to balance safety, speed, and scale.

Check yourself

Answer to earn rating on the learn ladder.

1. Why moderate at both ingestion and serving time?

2. What role do human reviewers play?

3. What is the core moderation tradeoff?