SQL vs NoSQL Decision Framework
The ultimate architecture selection rubric: 8 critical decision axes, hybrid polyglot persistence patterns, and why PostgreSQL is often the best default choice.
01.The 8 Critical Evaluation Axes for Database Selection
During system design interviews and architecture RFCs, evaluate these 8 architectural axes before selecting a database engine:
- Transactional Guarantee: Do you require strict ACID multi-row atomicity and foreign key referential integrity (e.g., banking, e-commerce checkout), or is eventual consistency (BASE) acceptable?
- Data Model Structure: Is data relational and tabular, hierarchical/document (JSON), graph/networked, or simple key-value pairs?
- Read vs Write Ratio: Is the system read-heavy (
100:1→Caching / Read Replicas) or write-heavy (1:10→LSM-Tree Cassandra/Kafka)? - Query Complexity: Do you need complex ad-hoc queries, aggregations (
GROUP BY), and multi-table joins, or strictly primary-key lookups? - Schema Stability: Is the schema well-defined and stable (SQL DDL), or rapidly evolving and polymorphic (JSON document)?
- Scale & Storage Volume: Will total data exceed 5 Terabytes, and write QPS exceed 50,000 writes/second (requiring horizontal sharding)?
- Latency SLAs: Do queries require sub-millisecond memory speed (<1ms
→Redis), or is 5–20ms acceptable (Disk RDBMS)? - Operational Maturity: Does your engineering team have the operational expertise to maintain distributed Cassandra/Kafka clusters?
The Enterprise Database Selection Decision Tree 🌳
The Enterprise Database Selection Decision Tree 🌳
Systematic architectural decision tree for choosing between Relational (PostgreSQL), Document (MongoDB), Wide-Column (Cassandra), Key-Value (Redis), and Graph (Neo4j) databases.
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