Use Cases

Find patterns by the kind of system you're building.

Web APIs & Microservices

Building a REST/gRPC service? These patterns keep it reliable under load.

Scenario	Patterns	Real Example
Protect against downstream outages	Circuit Breaker + Retry with Backoff	Netflix Hystrix wraps every HTTP client call
API rate limiting	Rate Limiter	Stripe allows burst of 25, refills at 25/sec
Request middleware (auth, logging, tracing)	Middleware Chain	gRPC interceptors, Koa.js onion model
Service discovery	Registry	Consul, etcd service registration
Load distribution across nodes	Consistent Hashing	HAProxy, groupcache key distribution
Prevent overload	Backpressure + Batch Processing	Node.js stream piping, Kafka consumer groups

Databases & Storage

The patterns behind PostgreSQL, Redis, LevelDB, and every serious storage engine.

Scenario	Patterns	Real Example
Crash recovery	WAL + Checkpointing	PostgreSQL: WAL + periodic checkpoint
Write-heavy workload	LSM Tree + Bloom Filter	LevelDB/RocksDB: memtable → SSTable + bloom skip
Range queries on disk	B+ Tree	PostgreSQL btree index, SQLite
Concurrent reads/writes	MVCC	PostgreSQL tuple versioning, etcd revisions
Data integrity verification	Merkle Tree	ZFS block checksums, Git object store
Sorted key merge	Merge Iterator + Min Heap	LevelDB compaction
Delete without immediate removal	Tombstone	Cassandra tombstones, LevelDB deletion markers
In-memory sorted set	Skip List	Redis ZADD/ZRANGE sorted sets
In-memory cache	LRU Cache	Redis LRU eviction, Go groupcache
Event ordering without clocks	Logical Clock	etcd Raft log, DynamoDB version vectors

Frontend & UI Frameworks

React, Vue, and browser engines use these patterns every frame.

Scenario	Patterns	Real Example
Virtual DOM diffing	Diff / Patch + Bitmask	React reconciler: diff tree, apply minimal patches
Responsive rendering	Cooperative Scheduling	React Scheduler: yield every 5ms to stay under 16ms
Frame-safe state updates	Double Buffering	React Fiber: workInProgress ↔ current tree swap
Avoid unnecessary re-renders	Dirty Flag	React shouldComponentUpdate, Chromium layout
State management	Observer + State Machine	Redux subscribe, XState finite states
Priority-based task scheduling	Min Heap	React Scheduler priority queue

Distributed Systems

Patterns for systems that span multiple machines.

Scenario	Patterns	Real Example
Consensus log	WAL + Logical Clock	etcd Raft: append-only log with term/index
Partition-tolerant routing	Consistent Hashing	Amazon DynamoDB, Cassandra ring
Replicated state	State Machine + WAL	Raft: replicated state machine via log
Conflict-free replication	Logical Clock + Tombstone	CRDTs, Dynamo-style last-write-wins
Data synchronization	Merkle Tree	Cassandra anti-entropy repair
Message-driven architecture	Actor Model + Backpressure	Akka cluster, Erlang/OTP
Build/deploy pipelines	Dependency Graph + Batch Processing	Cargo build graph, pnpm workspace

Runtime & Memory Management

How Go, CPython, V8, and game engines manage memory and execution.

Scenario	Patterns	Real Example
Reduce GC pressure	Object Pool + Free List	Go sync.Pool, Linux SLUB allocator
Phase-based allocation	Arena Allocator	Rust bumpalo, Go arena (experimental)
Deterministic cleanup	Reference Counting	CPython refcount, Rust Rc/Arc
String deduplication	Interning + Flyweight	Rust compiler symbol interning, Python small int cache
Efficient cloning	Copy-on-Write	Linux fork(), Rust Cow<T>
Work distribution across cores	Work Stealing	Go runtime P/M/G scheduler, Tokio
I/O multiplexing	Event Loop + Ring Buffer	libuv (Node.js), Redis single-thread
Thread-safe counters	Semaphore	Linux kernel semaphores, Go x/sync

Compilers & Language Tools

Patterns used in LLVM, V8, rustc, and the Vue/React compilers.

Scenario	Patterns	Real Example
AST traversal	Visitor	LLVM InstVisitor, Vue compiler transforms
Dynamic dispatch	Vtable	CPython tp_* slots, Rust dyn Trait
Symbol tables	Interning + Trie	rustc Symbol interning
IR transformations	Iterator + Diff / Patch	Rust Iterator adapters, tree-sitter edits
Type representation	Tagged Union	V8 tagged pointers, PyTorch TensorImpl
Plugin systems	Registry + Middleware Chain	Babel plugins, webpack loaders

Networking & Protocols

Scenario	Patterns	Real Example
Connection state tracking	State Machine	Linux TCP state machine (SYN_SENT → ESTABLISHED → ...)
IP routing	Trie	Linux LC-trie for IPv4 FIB
Packet buffering	Ring Buffer	Linux sk_buff, DPDK ring
Flow control	Backpressure + Rate Limiter	TCP flow control, Nginx limit_req
DNS resolution	Trie + LRU Cache	Domain name lookup + response cache