\subsection{Transactions}
Transactions are accesses to the database with the purpose of \textit{modifying the data}.
The focus is of course on correctness, recovery and state management.

Transactions typically are expensive compared to queries due to the focus on correctness.

This means we need to employ concurrency control (ensuring data remains consistent with transactions and queries running at the same time,
definition of consistency, correctness, conflicts and problematic situations, as well as locking).
We furthermore want to implement recovery, to ensure that data remains consistent even when unexpected failures occur.
