How would you design a search system (e.g. product or document search)?
⚡ Short Answer
Build an inverted index (term → list of documents) so queries are fast lookups, not full scans. Ingest documents through an analysis pipeline (tokenize, lowercase, stem), index them (Elasticsearch/OpenSearch), keep the index eventually consistent with the source via events, and rank results (TF-IDF/BM25 + business signals). Add pagination, filters, and typo tolerance.
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“How would you design a search system (e.g. product or document search)?”
🧠Mind Map Answer
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🔥What If?
Think Beyond the Expected
Why use Elasticsearch instead of SQL LIKE '%term%' for search?
LIKE '%term%' can't use an index (non-SARGable) → full table scan, no relevance ranking, no stemming/typo tolerance. An inverted index looks up matching docs in near-constant time and ranks them by relevance (BM25), with analyzers for stemming/synonyms — purpose-built for search where a relational LIKE collapses at scale.
😂Real World
Product/document search runs on Elasticsearch/OpenSearch fed asynchronously from the primary DB (CDC/events); the index is eventually consistent, and ranking blends text relevance with business signals (popularity, recency).
🎯Interviewer's Expectation
Keywords they're listening for:
⚠️Common Mistakes
- ✗SQL LIKE '%...%' for real search (full scans)
- ✗Synchronous indexing on the write path
- ✗Ignoring relevance ranking
✅Best Practices
- ✓Use an inverted index (Elasticsearch/OpenSearch)
- ✓Index asynchronously from the source of truth
- ✓Blend text relevance with business signals
🔁Follow-up Questions
- 1How do you keep the search index in sync with the DB?
- 2How does relevance ranking (TF-IDF/BM25) work?
- 3How do you add typo tolerance / autocomplete?
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Plain-language foundations
I'm preparing for a software engineering interview and want to understand this from scratch, as a beginner. Topic: Databases (System Design) Interview question: "How would you design a search system (e.g. product or document search)?" Please: 1. Explain the core idea in simple, plain language, using an everyday analogy. 2. Define any technical terms you use. 3. Walk through one small, concrete example. 4. Finish with a single sentence I can easily remember. Keep the tone friendly and assume I'm new to this topic.
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