How can the database operate under such load?

A database can operate efficiently under high load due to several key mechanisms:

• Indexing — proper indexes allow quick data retrieval without full table scans.
• Caching — data or query results can be stored in memory, reducing disk load.
• Parallelism and multithreading — DBMS can process multiple queries simultaneously using multi-processor systems.
• Query optimization — the query planner chooses the most efficient execution plan.
• Sharding and replication — distributing data across different servers and copying for load balancing and fault tolerance.

For example, in PostgreSQL, table partitioning and indexes supporting parallel query execution can significantly improve performance under load.