{"id":2012,"date":"2026-07-22T23:00:22","date_gmt":"2026-07-22T17:30:22","guid":{"rendered":"https:\/\/lastroundai.com\/blog\/?post_type=iq&p=2012"},"modified":"2026-07-21T20:29:48","modified_gmt":"2026-07-21T14:59:48","slug":"dynamodb","status":"publish","type":"iq","link":"https:\/\/lastroundai.com\/interview-questions\/dynamodb","title":{"rendered":"DynamoDB Interview Questions (2026): 51 Q&As"},"content":{"rendered":"

A backend candidate at a mid-size logistics company got asked to design a schema for tracking package scans, one write per scan event, tens of thousands of packages moving through a handful of regional hubs at once. He reached for a relational instinct: a packages table, a scans table, a foreign key between them. The interviewer’s follow-up killed it in one sentence: what happens when every package scanned at the same hub in the same hour writes to the same partition. That’s the DynamoDB interview in miniature. The service looks like a key-value store with a friendly API, and most of the actual difficulty lives in key design decisions you make before you write a single query. AWS’s own developer guide frames the whole service around exactly this tradeoff, since a table’s partition and sort keys determine how data physically spreads across storage nodes (AWS DynamoDB Developer Guide<\/a>).<\/p>\n

Here’s a take that might be unpopular: most DynamoDB prep spends too much time on the CRUD API surface, PutItem, GetItem, UpdateItem, and not enough on capacity planning and access-pattern modeling, which is where interviewers actually differentiate candidates. You can memorize every API call in an afternoon. Understanding why a hot partition throttles your whole table even though your account-level throughput looks fine takes actual hands-on scar tissue, or at minimum a careful read of how DynamoDB’s quotas work under the hood.<\/p>\n

This page covers eight areas: the core data model (tables, items, attributes, primary keys), partition keys and secondary indexes, capacity modes and throughput, read consistency and Query versus Scan, writes and transactions, Streams and TTL and global tables, single-table design and hot partition mitigation, and day-two operations like DAX, backups, and throttling. Questions run from the kind asked in a phone screen through the kind that shows up in a staff-level system design loop.<\/p>\n

51<\/span>Questions<\/span><\/div>
400 KB<\/span>Max Item Size<\/span><\/div>
20 per table<\/span>Default GSI Limit<\/span><\/div>
5 per table<\/span>Default LSI Limit<\/span><\/div><\/div>\n

Tables, items, and the primary key<\/h2>\n

Everything else on this page builds on how DynamoDB names and stores a single row. Get the vocabulary wrong here and the rest of the interview gets harder than it needs to be.<\/p>\n

<\/span>Easy questions<\/h2>13<\/span><\/div>
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