Borrowing it
Nothing to install: this file belongs to levifig/rails-instructions. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/levifig/rails-instructions/main/.github/instructions/rails-performance.instructions.mdgit clone --depth 1 https://github.com/levifig/rails-instructionsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/instructions/levifig/rails-instructions/rails-performance)<a href="https://agentmods.dev/instructions/levifig/rails-instructions/rails-performance"><img src="https://agentmods.dev/badge/instructions/levifig/rails-instructions/rails-performance/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/instructions/levifig/rails-instructions/rails-performance"><img src="https://agentmods.dev/badge/instructions/levifig/rails-instructions/rails-performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.01103 | $0.01103 |
| Opus 5.5 | $0.00441 | $0.00441 |
| Sonnet 5.5 | $0.00221 | $0.00221 |
| Haiku 4.5 | $0.00110 | $0.00110 |
Grade A, and why
rails-instructions rails-performance.instructions.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 238 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rails Performance Guide
Core Philosophy
- Measure before optimizing
- Optimize for the common case
- Keep solutions simple and maintainable
- Use Rails built-in performance features
- Monitor performance in production
Database Optimization Principles
- Design efficient schemas from the start
- Index foreign keys and queried columns
- Use database-specific features wisely
- Keep queries simple and focused
- Monitor slow query logs
Query Optimization
- Eliminate N+1 queries with includes
- Use select to limit returned columns
- Implement pagination for large datasets
- Use pluck for single column queries
- Batch process large operations
Indexing Strategy
- Index all foreign keys
- Create composite indexes for multi-column queries
- Use partial indexes for filtered queries
- Monitor index usage and effectiveness
- Remove unused indexes
Caching Principles
- Cache at multiple levels
- Use Russian doll caching for nested content
- Implement fragment caching for expensive views
- Cache database queries appropriately
- Monitor cache hit rates
Rails Cache Store
- Use Solid Cache for database-backed caching
- Configure Redis for high-traffic applications
- Set appropriate cache expiration
- Use cache keys that auto-expire
- Monitor cache memory usage
Fragment Caching
- Cache expensive view partials
- Use cache digests for automatic expiration
- Implement conditional caching
- Cache user-specific content carefully
- Profile view rendering times
Query Caching
- Leverage Rails query cache
- Use low-level caching for expensive calculations
- Cache aggregated data
- Implement counter caches
- Update caches strategically
Asset Optimization
- Use Propshaft for simple asset handling
- Implement CDN for asset delivery
- Compress assets appropriately
- Set proper cache headers
- Optimize image sizes
Background Job Performance
- Process heavy operations asynchronously
- Use appropriate queue priorities
- Batch similar operations
- Monitor job queue depth
- Implement job timeouts
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 238 lines · 1,103 tokens per session scan A 69734e64e38a
rails-instructions rails-performance.instructions.md is an instructions file published in the GitHub repository levifig/rails-instructions (56 stars, last pushed 1y ago), licensed MIT. It adds 1,103 tokens to every session, about $0.0044 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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