Online Transaction Processing - database systems optimized for handling many small transactions quickly. Like a busy cash register that processes hundreds of purchases efficiently.
E-commerce websites use OLTP databases to handle thousands of order transactions per minute.
OLTP is a workload pattern (many short, concurrent reads/writes with strong consistency). These managed relational database services are commonly used to run OLTP applications; each provides automated backups, scaling options, and high availability features suited to transactional systems.