Base64 includes +, /, and =, which are not safe for URLs:

• becomes a space in some contexts

/ can break paths

= is used for padding and may be misinterpreted

GSI: A GSI, or Global Secondary Index, is a DynamoDB feature that lets you query the table using non-primary key attributes, and it can span all partitions globally. DynamoDB is super-fast because it uses a partition key (and optional sort key) for primary lookups. But sometimes, you want to query by another field — you define a GSI — and DynamoDB will maintain a separate index for that. gives flexibility in querying through miltiple keys w/o deduping data in another table

howto use: https://hyp.is/9kEfBlN7EfCXVivplSZlYA/www.hellointerview.com/learn/system-design/problem-breakdowns/fb-news-feed