Fly.io vs Heroku

Fly.io and Heroku represent two distinct philosophies for database management. Fly.io operates with a lean, infrastructure-first approach, where PostgreSQL instances range from $1.94/mo for a tiny 0.256 GB RAM footprint up to $131.80/mo for 16 GB of memory. Heroku targets enterprise-scale requirements, with pricing that scales significantly higher, starting at $5.00/mo and reaching $1500.00/mo for massive 126 GB RAM allocations. While Fly.io relies on smaller, localized storage blocks topping out at 160 GB, Heroku offers deep storage tiers extending up to 2000 GB, catering to long-term data retention needs that would force a hard migration on smaller platforms.

• Fly.io charges a flat $0.15/GB for additional storage, while Heroku’s pricing model is baked into the instance tier, often requiring a move to a higher monthly commit to gain more disk space.
• Heroku provides significantly higher memory ceilings of 126 GB, which is necessary for complex query caching that would otherwise choke the 16 GB limit found on Fly.io.
• Fly.io enforces an overage penalty of $0.02/GB for network egress, a granular cost that Heroku typically abstracts away within its platform-level subscription tiers.
• Heroku’s high-end tiers utilize robust multi-AZ replication to handle heavy write loads, whereas Fly.io users are generally responsible for defining their own replication topology across regions.

Choosing between these two comes down to the specific hardware requirements of the workload. Fly.io is built for developers who want to manage raw compute resources and keep costs low for smaller, distributed applications, often competing with the pricing agility seen at providers like DigitalOcean. Heroku remains the standard for teams that prefer to pay for a managed ecosystem where memory, IOPS, and replication are handled as a black box, even if that leads to a much steeper monthly invoice as the database size grows.