Welcome to the DynamoDB Glossary. Here you will find definitions for common abbreviations and technical terms used throughout the course.

Example Usage: Hover over GSI to see the definition.

Core Concepts

Term	Full Name	Definition
Attribute	Attribute	A fundamental data element, something that does not need to be broken down any further. Analogous to a column in a relational database.
Composite Key	Composite Primary Key	A primary key composed of both a partition key and a sort key, allowing multiple items with the same partition key.
Consistent Hashing	Consistent Hashing	A technique used by DynamoDB to distribute data across partitions. It minimizes reorganization of data when nodes are added or removed.
Hash Key	Hash Key (Partition Key)	The first part of the primary key. DynamoDB uses the partition key’s value as input to an internal hash function. The output from the hash function determines the partition (physical storage internal to DynamoDB) in which the item is stored.
Hot Partition	Hot Partition	A partition that receives a disproportionate amount of read or write traffic, potentially leading to throttling if the traffic exceeds the partition’s throughput limits.
Item	Item	A collection of attributes. Each item is identifiable by a primary key. Items in DynamoDB are similar in many ways to rows, records, or tuples in other database systems.
On-Demand	On-Demand Capacity	A flexible billing option for DynamoDB capable of serving thousands of requests per second without capacity planning. You pay per request for the data reads and writes your application performs on your tables.
Partition Key	Partition Key	The primary key attribute used by DynamoDB to distribute data across partitions for scalability. Also known as the Hash Key.
Provisioned Mode	Provisioned Mode	A billing option where you specify the number of reads and writes per second that you require for your application. You can use auto-scaling to adjust your table’s provisioned capacity automatically in response to traffic changes.
Provisioned Throughput	Provisioned Throughput	The maximum amount of capacity (RCUs/WCUs) that an application can consume from a table or index.
RCU	Read Capacity Unit	One read capacity unit represents one strongly consistent read per second, or two eventually consistent reads per second, for an item up to 4 KB in size.
Sort Key	Sort Key (Range Key)	The second part of the primary key. If a table has a composite primary key (partition key and sort key), DynamoDB stores all the items with the same partition key value physically close together, sorted by the sort key value.
TTL	Time To Live	A mechanism that allows you to define a specific timestamp when an item is no longer needed. Shortly after the date and time of the specified timestamp, DynamoDB deletes the item from your table without consuming any write throughput.
WCU	Write Capacity Unit	One write capacity unit represents one write per second for an item up to 1 KB in size.

Indexes

Term	Full Name	Definition
GSI	Global Secondary Index	An index with a partition key and an optional sort key that can be different from those on the base table. GSIs allow you to query data across all partitions.
Item Collection	Item Collection	A group of items that share the same Partition Key but have different Sort Keys. Item collections allow related data to be retrieved in a single request using the Query operation.
LSI	Local Secondary Index	An index that has the same partition key as the base table but a different sort key. LSIs allow you to query data within a single partition using an alternative sort order.
Overloading	Index Overloading	A design pattern where a single GSI is used to index multiple different entity types by using generic key names (e.g., GSI1PK, GSI1SK).
Projection	Index Projection	The set of attributes that are copied (projected) from the base table into a secondary index.
Sparse Index	Sparse Index	An index that only contains items that have a value for the index’s sort key (or partition key). Items without the key are omitted.

Consistency & Operations

Term	Full Name	Definition
BatchWriteItem	BatchWriteItem	An operation that puts or deletes multiple items in one or more tables. It does not provide atomicity across items.
Conditional Write	Conditional Write	A write operation that succeeds only if the item attributes meet one or more expected conditions.
Condition Expression	Condition Expression	An expression used in PutItem, UpdateItem, or DeleteItem to specify conditions that must be met for the operation to succeed (optimistic locking).
Consistent Read	Consistent Read	A read operation that returns the most up-to-date data, reflecting all successful write operations that occurred before the read. Consumes 2x the capacity units of an eventually consistent read.
Eventual Consistency	Eventual Consistency	The default consistency model for DynamoDB read operations. When you read data from a DynamoDB table, the response might not reflect the results of a recently completed write operation.
Filter Expression	Filter Expression	An expression used in Query or Scan to filter the results after they have been read from the table but before they are returned to the client.
Query	Query Operation	An operation that finds items based on primary key values. Highly efficient compared to Scan.
Scan	Scan Operation	An operation that reads every item in a table or secondary index. Generally inefficient for large tables.
Strong Consistency	Strong Consistency	A read consistency model that guarantees that a read returns the most recent write.
Transaction	TransactWriteItems	An API operation that groups up to 100 actions into a single all-or-nothing operation with ACID properties.

Advanced Patterns

Term	Full Name	Definition
Access Pattern	Access Pattern	The specific query or operation an application needs to perform on the database. In DynamoDB, schema design begins with identifying all access patterns first, rather than modeling the data structure first.
Adaptive Capacity	Adaptive Capacity	A feature that automatically isolates frequently accessed items on a partition and re-balances them to other partitions to prevent hot partitions.
Adjacency List	Adjacency List Pattern	A design pattern used to model many-to-many relationships in DynamoDB. It involves storing each relationship as an individual item, allowing for efficient querying of related entities.
DAX	DynamoDB Accelerator	A fully managed, highly available, in-memory cache for DynamoDB that delivers up to a 10x performance improvement.
DynamoDB Streams	DynamoDB Streams	An optional feature that captures a time-ordered sequence of item-level modifications in a DynamoDB table and stores this information for up to 24 hours.
GSI Sharding	GSI Sharding	A technique where a GSI partition key is computed (e.g., Status_0, Status_1) to avoid hot partitions on low-cardinality attributes.
Single Table Design	Single Table Design	A design philosophy where multiple entity types (e.g., Users, Orders, Products) are stored in a single DynamoDB table. This optimizes for performance by enabling the retrieval of heterogeneous items in a single request.
Streams	DynamoDB Streams	A feature that captures a time-ordered sequence of item-level modifications in a DynamoDB table and stores this information for up to 24 hours.
Write Sharding	Write Sharding	A technique to distribute writes across multiple partitions when a single partition key becomes a hot spot. It involves appending a random suffix to the partition key.