Connection Pool
A cache of reusable database connections that avoids the overhead of opening and closing a new connection for every query. Critical for high-throughput applications.
What is Connection Pool?
A cache of reusable database connections that avoids the overhead of opening and closing a new connection for every query. Critical for high-throughput applications.
Connection Pool is a foundational concept that sits in the Database Fundamentals area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "Connection Pool" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
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Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the Connection Pool lessonRelated lessons
Lessons that touch on Connection Pool as part of a larger topic.
Thread Pooling
Reuse threads instead of creating them, the pattern that makes web servers handle thousands of concurrent connections
advanced · consistency models
Database Connection Pooling
PgBouncer, HikariCP, and why opening a new database connection per request is a recipe for disaster
foundation · database fundamentals
Connection Reuse
Pool and reuse connections across your application to maximize throughput and minimize overhead
intermediate · api design protocols
Network Optimization
Reduce latency and bandwidth usage, compression, connection pooling, and protocol tuning
advanced · reliability resilience
Ambassador Container Pattern
A specialized sidecar that handles outbound connectivity, connection pooling, retries, and protocol translation for external services
intermediate · microservices architecture
See also
Related glossary terms you might want to look up next.
Database
An organized collection of data that can be easily accessed, managed, and updated. The backbone of almost every application.
ORM
Object-Relational Mapping: a library that lets you interact with a database using your programming language's objects instead of raw SQL. Drizzle, Prisma, and SQLAlchemy are ORMs.
Throughput
The number of operations a system can handle per unit of time. Think of it as how many cars a highway can move per hour.