golang-samber-hot

The saved excerpt is a snapshot from when this skill was listed. The external source remains the complete and most current version.

---
name: golang-samber-hot
description: "In-memory caching in Golang using samber/hot — eviction algorithms (LRU, LFU, TinyLFU, W-TinyLFU, S3FIFO, ARC, TwoQueue, SIEVE, FIFO), TTL, cache loaders, sharding, stale-while-revalidate, missing key caching, and Prometheus metrics. Apply when using or adopting samber/hot, when the codebase imports github.com/samber/hot, or when the project repeatedly loads the same medium-to-low cardinality resources at high frequency and needs to reduce latency or backend pressure."
user-invocable: true
license: MIT
compatibility: Designed for Claude Code, Codex or similar harness, and for projects using Golang.
metadata:
  author: samber
  version: "1.1.2"
  openclaw:
    emoji: "🔥"
    homepage: https://github.com/samber/cc-skills-golang
    requires:
      bins:
        - go
    install: []
    skill-library-version: "0.13.0"
allowed-tools: Read Edit Write Glob Grep Bash(go:*) Bash(golangci-lint:*) Bash(git:*) Agent WebFetch mcp__context7__resolve-library-id mcp__context7__query-docs AskUserQuestion Bash(godig:*) Bash(gopls:*) LSP mcp__gopls__*
paths:
  - "**/*.go"
---

**Persona:** You are a Go engineer who treats caching as a system design decision. You choose eviction algorithms based on measured access patterns, size caches from working-set data, and always plan for expiration, loader failures, and monitoring.

# Using samber/hot for In-Memory Caching in Go

Generic, type-safe in-memory caching library for Go 1.22+ with 9 eviction algorithms, TTL, loader chains with singleflight deduplication, sharding, stale-while-revalidate, and Prometheus metrics.

**Official Resources:**

- [pkg.go.dev/github.com/samber/hot](https://pkg.go.dev/github.com/samber/hot)
- [github.com/samber/hot](https://github.com/samber/hot)

This skill is not exhaustive — refer to library documentation and code examples for more information:

- For Go package docs, symbols, versions, importers, and known vulnerabilities, → See `samber/cc-skills-golang@golang-pkg-go-dev` skill (`godig`), preferred over Context7 for Go package facts.
- To navigate this library's usage in your own code (definitions, call sites, diagnostics), → See `samber/cc-skills-golang@golang-gopls` skill (`gopls`).
- Context7 remains a fallback for docs not indexed on pkg.go.dev.

```bash
go get -u github.com/samber/hot
```

## Algorithm Selection

Pick based on your access pattern — the wrong algorithm wastes memory or tanks hit rate.

| Algorithm | Constant | Best for | Avoid when |
| --- | --- | --- | --- |
| **W-TinyLFU** | `hot.WTinyLFU` | General-purpose, mixed workloads (default) | You need simplicity for debugging |
| **LRU** | `hot.LRU` | Recency-dominated (sessions, recent queries) | Frequency matters (scan pollution evicts hot items) |
| **LFU** | `hot.LFU` | Frequency-dominated (popular products, DNS) | Access patterns shift (stale popular items never evict) |
| **TinyLFU** | `hot.TinyLFU` | Read-heavy with frequency bias | Write-heavy (admission filter overhead) |
| **S3FIFO** | `hot.S3FIFO` | High throughput, scan-resistant | Small caches (<1000 items) |
| **ARC** | `hot.ARC` | Self-tuning, unknown patterns | Memory-constrained (2x tracking overhead) |
| **TwoQueue** | `hot.TwoQueue` | Mixed with hot/cold split | Tuning complexity is unacceptable |
| **SIEVE** | `hot.SIEVE` | Simple scan-resistant LRU alternative | Highly skewed access patterns |
| **FIFO** | `hot.FIFO` | Simple, predictable eviction order | Hit rate matters (no frequency/recency awareness) |

**Decision shortcut:** Start with `hot.WTinyLFU`. Switch only when profiling shows the miss rate is too high for your SLO.

For detailed algorithm comparison, benchmarks, and a decision tree, see [Algorithm Guide](./references/algorithm-guide.md).

## Core Usage

### Basic Cache with TTL

```go
import "github.com/samber/hot"

cache := hot.NewHotCache[string, *User](hot.WTinyLFU, 10_000).
    WithTTL(5 * time.Minute).
    WithJanitor().
    Build()
defer cache.StopJanitor()

cache.Set("