Real-time database

Real-time database has two meanings. The most common use of the term refers to a database system which uses streaming technologies to handle workloads whose state is constantly changing.^[1] This differs from traditional databases containing persistent data, mostly unaffected by time. When referring to streaming technologies, real-time processing means that a transaction is processed fast enough for the result to come back and be acted on right away.^[2] Such real-time databases are useful for assisting social media platforms in the removal of fake news, in-store surveillance cameras identifying potential shoplifters by their behavior/movements, etc.

The second meaning of the term “real-time database” adheres to a stricter definition of real-time consistent with Real-time computing. Hard real-time database systems work with a real-time operating system to ensure the temporal validity of data through the enforcement of database transaction deadlines and include a mechanism (such as transaction scheduling policies) to maximize the number of successfully committed transactions and minimize the number of rolled-back transactions. While the performance metric for most database systems is throughput or transactions-per-second, the performance metric of a hard real-time database system is the ratio of committed-to-aborted transactions. This ratio indicates how effective the transaction scheduling policy is, with the ultimate goal of meeting deadlines 100% of the time. Hard real-time databases, through enforcement of deadlines, may not allow transactions to be late (overrun the deadline).^[3]