What is database replication and what is it used for? What problems can arise?

Database replication is the process of copying and maintaining synchronization of data between multiple servers or database instances.

Why replication is needed:

• Increased fault tolerance (if the primary server fails, you can switch to a replica)
• Load distribution for reading (replicas handle read requests)
• Geographic distribution of data to reduce latency

Problems that may arise:

• Synchronization delay (replicas may be outdated at the time of reading)
• Conflicts during write operations in multi-master replication
• Increased complexity of administration and monitoring

Example: in PostgreSQL, streaming replication can be configured, where the primary server sends WAL records to replicas for synchronization.