A comprehensive performance comparison between PostgreSQL and MongoDB covering write and read operations across different data sizes (1k, 100k, 1M records). The benchmarks test both unoptimized and heavily tuned configurations, revealing PostgreSQL's superior performance in most scenarios including JSON operations where MongoDB traditionally excels. Key findings show PostgreSQL outperforming MongoDB in read operations by 2-94x depending on query type, while MongoDB shows advantages in write operations only when safety guarantees are disabled.