Glossary
Every term used across the URL Shortener journey — with a one-line definition, a deep dive on WHY it matters, a concrete example, and links to the chapter that defends it.
How to use this glossary: Search by term or scan a category. Each entry has an example (concrete number or snippet) and links to the chapter(s) where the term is introduced. Cross-references let you dive from term to term. External links (RFCs, papers, docs) are provided where relevant.
Estimation & scale
Back-of-envelope math for RPS, storage, bandwidth, and cost.
HTTP & redirects
Status codes, caching semantics, and why 301 vs 302 matters.
API design
REST decisions, idempotency, versioning, auth, rate limits.
Data model
Schema, primary keys, indexes, storage growth.
Short-code generation
The 5 approaches, collision math, Base62, Snowflake.
Caching
Cache patterns, TTL, invalidation, stampede protection.
Database
MySQL, MySQL, DynamoDB, Cassandra — head-to-head on this workload.
Distributed systems
Sharding, replication, consensus, consistency models.
Analytics
Event pipeline, batch vs stream, cardinality, retention.
Operations
Failure modes, on-call, observability, runbooks.
Security & abuse
Phishing, malware, DDoS, GDPR, rate-limit abuse.
Business
Cost, ROI, build-vs-buy, market positioning.
Ready to apply these?
Return to the URL Shortener journey and see every term in context.