Careeroza

What is a Vector Index

Search by Meaning

A vector database (or vector index) stores many embeddings together with the original text and metadata, and answers one question fast: which stored vectors are closest to this query vector? This is semantic search: "phone heating up while charging" finds the help article "Battery temperature issues" even without shared words (with a real embedding model).

indexing (once):   document ──► embedding model ──► vector ──► store (vector + text + metadata)
searching:         query    ──► embedding model ──► vector ──► nearest vectors ──► results

A Tiny Vector Store

Example

A complete in-memory vector store in about 30 lines. The hashed bag-of-words embed() from the Embeddings module stands in for a real embedding model:

import hashlib, math, re

def embed(text, dim=64):
    v = [0.0] * dim
    for w in re.findall(r"[a-z0-9]+", text.lower()):
        h = int(hashlib.md5(w.encode()).hexdigest(), 16)
        v[h % dim] += 1.0 if (h >> 8) % 2 == 0 else -1.0
    n = math.sqrt(sum(x * x for x in v)) or 1.0
    return [x / n for x in v]

class VectorStore:
    def __init__(self):
        self.items = []                         # (id, vector, text, metadata)

    def add(self, id, text, metadata=None):
        self.items.append((id, embed(text), text, metadata or {}))

    def search(self, query, k=3):
        q = embed(query)
        scored = [(sum(a * b for a, b in zip(q, v)), id, text) for id, v, text, _ in self.items]
        return sorted(scored, reverse=True)[:k]

store = VectorStore()
store.add("faq-1", "How long does a refund take? Refunds take 5-7 working days.")
store.add("faq-2", "Delivery usually takes 3-5 days in metro cities.")
store.add("faq-3", "You can cancel an order before it is shipped.")
store.add("faq-4", "Exchange clothes for a different size within 10 days.")

for score, id, text in store.search("how many days for refund", k=2):
    print(f"{score:.3f}  {id}  {text}")

Output

0.359  faq-1  How long does a refund take? Refunds take 5-7 working days.
0.298  faq-4  Exchange clothes for a different size within 10 days.