back-of-the-envelope

Estimate QPS, storage, bandwidth, and server count from scale inputs.

Updated Jul 5, 2026

Search Tags:#system design #estimation #capacity planning #storage #QPS

Ready to run

npx skills add https://github.com/Arupbiswas09/claude_skills --skill back-of-the-envelope

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: back-of-the-envelope
Source: https://github.com/Arupbiswas09/claude_skills/tree/main/skills/back-of-the-envelope
Command: npx skills add https://github.com/Arupbiswas09/claude_skills --skill back-of-the-envelope

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes scripts (resource) and references (resource) components.

What problem does it solve?

This Skill helps users estimate key system design parameters such as QPS, storage, bandwidth, and server count based on high-level scale inputs.

Core Features & Use Cases

Estimate QPS: Calculate the expected query per second rate for a system.
Storage and Bandwidth: Estimate daily and total storage needs and peak bandwidth requirements.
Server Count: Determine the number of servers needed based on peak QPS and per-server QPS rates.
Use Case: When planning a new system, use this Skill to estimate the required resources based on expected user activity and data volume.

Quick Start

Run the 'back-of-the-envelope' calculator with your specific parameters, e.g., python3 scripts/botec.py --dau 1000000 --actions 1 --peak 2 --obj-bytes 1000 --media-frac 0.5 --retention-days 365 --server-qps 1000.

Frequently Asked Questions about back-of-the-envelope

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How do I estimate server count and QPS for system design capacity planning?▼

System design capacity planning estimates server count and QPS by calculating peak query rates and dividing by per-server QPS capacity. This Skill processes high-level scale inputs like daily active users and action rates to determine required infrastructure resources.

What is back-of-the-envelope estimation for storage and bandwidth in system design?▼

Back-of-the-envelope estimation provides rough calculations for system design storage and bandwidth requirements. It multiplies user activity metrics by object sizes and retention periods to approximate daily storage needs and peak bandwidth consumption for initial feasibility checks.

How do I calculate storage requirements for a new system based on user activity?▼

Calculate storage requirements by multiplying daily active users by average actions per user, object size in bytes, and retention days. This Skill automates that computation, factoring in media fractions to differentiate text and media storage growth over time.

Can I use this capacity planning tool for initial feasibility checks without detailed architecture?▼

Yes, you can use this estimation tool for initial feasibility checks without detailed architecture. It requires only high-level scale inputs such as daily active users, peak multipliers, and object sizes to generate approximate QPS, storage, bandwidth, and server count metrics.

What inputs do I need to estimate peak bandwidth and QPS for system design?▼

To estimate peak bandwidth and QPS, you need daily active users, actions per user, peak multipliers, and object byte sizes. The Skill uses these parameters to calculate expected query rates and multiply them by data sizes for bandwidth projections.

When should I not use rough capacity planning estimates for system design?▼

Avoid using rough capacity planning estimates when precise resource allocation or architectural validation is required. These calculations provide initial feasibility approximations rather than production-grade benchmarks, meaning detailed performance testing should follow preliminary estimations.