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Database Selection Guide
Master the art of choosing the right database for any system design scenario.
45 minutes
11Detailed Sections
Senior Level
A comprehensive comparison of popular databases across key system design dimensions.
Comparison Table
| DB / System | Role | Scale (ops/sec) | Consistency | Latency | Best For |
|---|---|---|---|---|---|
| PostgreSQL | OLTP | 10k–1M+ | Strong ACID | Low ms | Core transactional systems, payments, ledgers |
| MySQL | OLTP | 10k–100k+ | Strong ACID | Low ms | Web backends, payments, legacy fintech |
| Oracle | OLTP/OLAP | 100k+ | Strong ACID | Low ms | Core banking, card processing, data hubs |
| CockroachDB | OLTP (Dist) | Hundreds of k | Strong ACID | Low ms (Net) | Global consistency, regional residency |
| ClickHouse | OLAP | Millions | Analytical | Sub-second | Trade analytics, risk, dashboards |
| kdb+ | OLAP (TS) | Millions+ | Strong (Proc) | Microsecond | HFT tick data, real-time market analytics |
| Cassandra | OLTP (Wide) | Millions | Tunable / AP | Single ms | Event logs, telemetry, risk/fraud events |
| MongoDB | OLTP (Doc) | 100k+ | Strong (Majority) | Low ms | Customer data, content, microservices |
| Redis | OLTP (KV) | 1M+ | Strong (Key) | Sub-ms | Caching, sessions, rate-limiting |
| Kafka | Log/Stream | Millions+ | Durable log | Low ms | Event pipelines, CDC, audit logs |
| Geohash/S2 | Indexing | High | Eventual | Low ms | Uber/Lyft, proximity search at scale |
| Quadtree | Indexing | Very High | Strong (In-Mem) | Microsecond | Yelp, real-time spatial discovery |
| Dgraph | Graph (Dist) | High | Strong ACID | Low ms | Social graphs, GraphQL-native apps |