# Fly.io Billing and Cost Analysis at 500 Groups

_____

This article examines the infrastructure cost implications of scaling NGX Ramblers to 500 groups under both the current per-app model and the proposed single-instance model.

## Current Fly.io Billing Model

Fly.io does not charge for a single 512MB shared-CPU machine — the cost falls under their $5/month free allowance per app. Under the current per-app deployment model, each group's app stays below this threshold, so **13 deployments currently incur zero Fly.io compute charges**.

At 500 groups, the same maths applies per app — each 512MB machine is individually free.

## The 500-App Question

However, this raises a legitimate concern: **500 separate apps each exploiting the free allowance is qualitatively different from 13.** While Fly.io's pricing technically permits this, a large organisation like Ramblers deliberately provisioning 500 free-tier apps to avoid consolidated billing could be viewed as gaming the system.

Fly.io's fair use policies or terms of service may not endorse this at scale, and it would be prudent to clarify with Fly.io directly before committing to a 500-app strategy. If Fly.io were to revise their free-tier policy or flag the account, the cost picture would change dramatically — 500 apps at even $5/month each would be **$2,500/month**.

By contrast, a single-instance deployment would have clearly predictable and transparent costs — you pay for what you use, with no ambiguity about billing intent.

## Cost Comparison

| Resource | Current (13 groups) | Per-app at 500 groups | Single-instance at 500 groups |
|----------|--------------------|-----------------------|-------------------------------|
| Fly.io compute | 13 apps × 512MB (under $5 threshold) | 500 apps × 512MB (under $5 threshold*) | 2–4 instances × 2–4GB |
| Fly.io cost | **$0/month** | **$0/month** (or $2,500 if policy changes*) | ~$50–80/month |
| MongoDB Atlas | M10 shared, 13 DBs | M30+ dedicated, 500 DBs | M30+ dedicated, 500 DBs |
| MongoDB cost | **$0/month** (free tier) | ~$600/month | ~$600/month |
| S3 buckets | 13 buckets | 500 buckets | 1 bucket, 500 prefixes |

_*Per-app free tier at 500 apps is technically possible but may not be sustainable or endorsed by Fly.io at this scale._

## Key Takeaway

The current model's zero Fly.io cost is a genuine advantage — but it depends on a pricing model that may not hold at 500 apps. A large organisation like Ramblers would likely prefer a clean, transparent billing relationship with infrastructure providers rather than relying on free-tier arbitrage at scale.