Streaming data analysis has recently attracted attention in numerous applications including telephone records, network streams, financial records etc. Such applications require continuous storing of terabytes of streaming data while simultaneously providing good response times for the queries against the data already stored into the system. The duration and amount of data stored into the system varies from use-case to use-case. It may vary from one week to one year to tens of years. The performance estimates presented in this paper would help in understanding what to expect from two widely used open source RDBMS, MySQL and PostgreSQL, in terms of data insertion rates, indexing time, data sizes, index sizes and query performance.