Teach feeds after the simple feed has limits.

Goal

Make feed quality a visible product decision.

This phase teaches that ranking is not magic. It is a set of product choices, data inputs, cost constraints, and tradeoffs between freshness and relevance.

Build

• Hot ranking with score and age.
• Subscribed feed based on joined communities.
• Basic recommendation signals for communities.
• Batch updates or materialized views for expensive rankings.

Concepts

• Ranking algorithms.
• Time decay.
• Batch jobs.
• Materialized views.
• Freshness versus cost.

Prompt stub

Add a simple hot ranking sort.
Use score and post age.
Explain the formula and its tradeoffs in beginner language.
Do not add machine learning or complex recommendations yet.

Done means

• Users can browse newest, top, hot, and subscribed feeds.
• The hot ranking formula is simple and explainable.
• Expensive feed work is measured before being optimized.
• The learner can describe why ranking changes user behavior.