Glossary
Key terms used across all articles. Hover definitions are injected via <abbr> tags in each page using the abbr markdown extension.
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*[ACID]: Atomicity, Consistency, Isolation, Durability — the four properties of reliable transactions.
*[CAP]: Consistency, Availability, Partition Tolerance — only two can be guaranteed at once.
Full Term Reference
| Term | Definition |
|---|---|
| ACID | Atomicity, Consistency, Isolation, Durability — transactional guarantees |
| BASE | Basically Available, Soft state, Eventually consistent — NoSQL alternative to ACID |
| CAP Theorem | A distributed system can guarantee at most two of: Consistency, Availability, Partition Tolerance |
| Sharding | Horizontal partitioning of data across multiple nodes |
| Replication | Copying data to multiple nodes for availability and fault tolerance |
| WAL | Write-Ahead Log — durability mechanism; changes logged before applying |
| LSM Tree | Log-Structured Merge Tree — write-optimized storage engine |
| B-Tree | Balanced tree — read-optimized storage engine used in most RDBMS |
| Bloom Filter | Probabilistic data structure to test if an element is in a set |
| Quorum | Minimum number of nodes that must agree for an operation to succeed |
| 2PC | Two-Phase Commit — distributed atomic commit protocol |
| CDC | Change Data Capture — streaming DB changes to downstream consumers |
| Saga | Distributed transaction pattern using compensating transactions |
| Materialized View | Precomputed and stored query result, refreshed periodically |
| Consistent Hashing | Hash ring technique to distribute keys with minimal remapping on node changes |
| Eventual Consistency | Consistency model where replicas converge over time without guaranteeing immediate consistency |
| Isolation Level | Degree to which concurrent transactions are isolated from each other |
| Read Replica | A copy of the primary database serving only read traffic |
| Normalization | Process of organizing DB schema to reduce redundancy |
| Index | Data structure that speeds up read queries at the cost of write overhead |
| Partition Tolerance | System continues operating despite network partitions |
| Spanner | Google Cloud Spanner — globally distributed, strongly consistent SQL database |
| BigQuery | Google BigQuery — serverless, highly scalable analytics data warehouse |
| DynamoDB | Amazon DynamoDB — managed NoSQL key-value and document database |
| Cassandra | Apache Cassandra — wide-column store optimized for high write throughput |
| MongoDB | Document-oriented NoSQL database with flexible schema |
| PostgreSQL | Open-source relational database with strong ACID compliance |
| Redis | In-memory data structure store, used as cache, message broker, and queue |