DynamoDB Query a GSI in Python (boto3)

Querying a global secondary index is a normal query plus one parameter: IndexName. The key condition then targets the index's keys, not the table's — here AlbumTitle-index lets us fetch songs by album, an access pattern the base table (Artist + SongTitle) can't serve without a scan.

Code

import boto3

client = boto3.client("dynamodb")

paginator = client.get_paginator("query")

items = []
for page in paginator.paginate(
    TableName="Music",
    IndexName="AlbumTitle-index",
    KeyConditionExpression="#hashKey = :hashKeyValue",
    ExpressionAttributeNames={"#hashKey": "AlbumTitle"},
    ExpressionAttributeValues={":hashKeyValue": {"S": "Danzon"}},
):
    items.extend(page["Items"])

print(f"Found {len(items)} songs on the album")

Explanation

• IndexName — names the GSI to query (TableName is still required). The KeyConditionExpression uses the index's partition (and optional sort) key — AlbumTitle here — with the same operators as a table query.
• Eventual consistency only — GSIs replicate from the base table asynchronously. Passing ConsistentRead=True on a GSI query doesn't upgrade it; it raises a ValidationException. (Local secondary indexes do support strong consistency.)
• You get projected attributes only — a GSI query returns what the index projects (ALL, KEYS_ONLY, or INCLUDE-listed attributes) and cannot fetch the rest from the base table. Need an unprojected attribute? Follow up with get_item on the table key, or widen the projection.
• Keys aren't unique in a GSI — many items can share the same index key, and items missing the index key attribute simply don't appear (that's the sparse-index pattern).
• Pagination — client.get_paginator("query") follows LastEvaluatedKey across pages exactly as on a table query; each page carries an Items list.
• On the resource API, the same query is table.query(IndexName="AlbumTitle-index", KeyConditionExpression=Key("AlbumTitle").eq("Danzon")) with native Python values.

Do it visually

The DynamoDB Expression Builder builds the key condition + name/value maps for index queries and copies runnable boto3 code.

To browse a table's indexes and run GSI queries from a form — paginated grid, copy-as-code — download DynoTable.

Related examples

• DynamoDB Query a GSI in Node.js — the same index query with AWS SDK v3.
• DynamoDB Query a GSI with the AWS CLI — the same index query from the shell.
• DynamoDB Query in Python — querying the base table.
• GSI vs. LSI — which index type fits the access pattern.
• Why GSIs are eventually consistent — the replication lag explained.
• "The table does not have the specified index" — the index name doesn't match (GSI names are case-sensitive).
• "Consistent reads are not supported on global secondary indexes" — why the consistent-read flag fails on a GSI.

References

• Query — Amazon DynamoDB API Reference
• DynamoDB.Paginator.Query — Boto3 documentation
• Using Global Secondary Indexes in DynamoDB — Amazon DynamoDB Developer Guide

Last verified 2026-07-13 against the official AWS documentation linked above.