System Design Vocabulary

System design interviews test whether you can design scalable, reliable systems. The vocabulary is critical.

Term	Meaning
scalability	Ability to handle growing load
availability	Percentage of time system is operational (99.9% = 8.7h downtime/year)
fault tolerance	Continuing to function despite component failures
redundancy	Duplicate components to prevent single points of failure
replication	Copying data across multiple nodes
sharding	Splitting a database horizontally across multiple nodes
CDN	Content Delivery Network — serving static assets from edge locations

"To handle 1M requests/day, I would introduce a load balancer in front of the API tier."
"We can shard the database by user_id to distribute the write load."
"A CDN would serve static assets, reducing latency for global users."
"To avoid a single point of failure, we replicate the database across three availability zones."

Проверь себя