Why Vector DBs are used instead of traditional databases to store vector data
Two core reasons why vector databases are fundamentally different from traditional relational databases.
✅ 1. Binary Search Doesn’t Scale to High Dimensions
Traditional Indexing (Relational DBs):
- Uses B-trees or hash indexes on 1D scalar fields (like integers, names, timestamps).
- Search is fast because of ordering — e.g., binary search in a sorted list is O(log n).
Problem in Vector Space:
- A 2D+ vector doesn’t have a linear ordering.
- In 768D space, you can’t “sort” vectors or do binary search because:
- There’s no concept of greater/lesser in multiple directions.
- Similarity is measured by angles or distances, not order.
Hence, binary search, B-trees, and hash indexes are useless here.
🧠 What Vector DBs Do Instead:
They use Approximate Nearest Neighbor (ANN) algorithms like:
- HNSW (Hierarchical Navigable Small World)
- IVF (Inverted File Index)
- PQ (Product Quantization)
These algorithms structure the vector space in a way that lets you quickly find the most similar vectors without scanning them all — even in millions.
✅ 2. ACID Compliance Is Overkill for Vector Workloads
Relational DBs:
- Built for data integrity, with strict ACID guarantees:
- Atomicity: all-or-nothing transactions
- Consistency, Isolation, Durability
Great for:
- Banking systems
- Inventory tracking
- Critical business apps
Vector DBs:
- Most use cases don’t need full ACID:
- Embedding search
- Semantic recommendation
- Similar image/doc retrieval
These are mostly read-heavy, and eventual consistency or light durability is enough.
Plus, enforcing ACID would slow down high-throughput similarity search.
🔚 So to summarize your point, expanded:
✅ Relational DBs are great for structured, exact-match data with high consistency needs.
❌ They don’t scale to vector math — because there’s no sorting, no scalar index, and no need for strict ACID guarantees.
Meanwhile:
✅ Vector DBs are optimized for fast, similarity-based retrieval, often at web-scale, where approximate is good enough and speed is king.
