Is Amazon RDS cheaper than Cloud SQL?
When you are choosing where to host Postgres, price is rarely the only thing that matters, but it is often what decides it. And "cheaper" is slippery, so to be precise: here it means the real monthly bill to run the same workload on each service, worked out from published rates, not a sticker price or an intro discount.
For Amazon RDS versus Cloud SQL, there is no single answer, because they bill on different models. Amazon RDS is per instance-hour, 24/7, no scale-to-zero. Cloud SQL is per vCPU-hour + per GB-RAM-hour, 24/7. Which one wins comes down to how big an instance you need.
So this page settles it with real numbers: we compute the monthly bill for Amazon RDS and Cloud SQL across a range of usage, find the exact point where the cheaper option flips, then look past price at the tradeoffs that decide a real migration. Prices were last verified 2026-08-01.
Short answer: Amazon RDS is cheaper at smaller sizes, up to about 1.2 CU. Above that, Cloud SQL is cheaper.
- The break-even point, charted
- What tips the balance between them
- Each provider's real gotchas and tradeoffs
- Which one to choose
- A calculator for your exact numbers
Where the answer flips
This matchup turns on how big an instance you need. The chart plots each provider’s monthly bill as that changes, holding always-on, at 25 GB storage. They cross at about 1.2 CU.
What tips the balance
They price out differently because of how each one bills. Amazon RDS: Per instance-hour, billed around the clock with no scale-to-zero. On-demand is the expensive default; Reserved Instances or Database Savings Plans cut roughly 30% to 70% for steady workloads.
Cloud SQL: Priced per vCPU-hour and per GB of RAM-hour separately, billed around the clock with no scale-to-zero. Committed-use discounts cut compute by about 25% for one year or 52% for three years.
So the honest answer is not a single number, it is a curve. Amazon RDS is cheaper at smaller sizes, up to about 1.2 CU. Above that, Cloud SQL is cheaper. The one gotcha that catches people on Amazon RDS: Multi-AZ high availability is a single checkbox that runs a full standby you also pay for, doubling the compute bill for a node that serves no read traffic. Stopping an instance still bills storage and backups, and RDS auto-restarts anything left stopped for 7 days. On Cloud SQL: RAM is a separate line item, so memory-heavy tiers cost more than people budget for, and RAM can end up the larger half of the bill. Turning on regional high availability roughly doubles the compute cost and raises the storage rate.
Beyond price: the two, side by side
Price is only half the decision. Here is what each one is actually like to run.
Amazon RDS
Per instance-hour, billed around the clock with no scale-to-zero. On-demand is the expensive default; Reserved Instances or Database Savings Plans cut roughly 30% to 70% for steady workloads.
Multi-AZ high availability is a single checkbox that runs a full standby you also pay for, doubling the compute bill for a node that serves no read traffic. Stopping an instance still bills storage and backups, and RDS auto-restarts anything left stopped for 7 days.
- Native AWS integration: IAM auth, Secrets Manager, VPC isolation, Performance Insights.
- Multi-AZ adds a synchronous standby with automatic failover, at roughly 2x compute.
- Up to 15 read replicas, each a full paid instance.
- Provisioned storage bills whether used or not, and can only grow, never shrink.
- You own the patching cadence through weekly maintenance windows.
From a Mac client: Default max_connections scales with instance memory, roughly 80 to 100 on a db.t4g.micro, so a small instance is easy to exhaust. RDS Proxy adds managed pooling for about $22/mo per 2 vCPU.
Cloud SQL
Priced per vCPU-hour and per GB of RAM-hour separately, billed around the clock with no scale-to-zero. Committed-use discounts cut compute by about 25% for one year or 52% for three years.
RAM is a separate line item, so memory-heavy tiers cost more than people budget for, and RAM can end up the larger half of the bill. Turning on regional high availability roughly doubles the compute cost and raises the storage rate.
- Deep GCP integration: IAM database auth, the Auth Proxy, free same-region egress.
- Regional HA stands up a synchronous standby, at roughly 2x compute.
- Read replicas each bill as a full separate instance.
- Committed-use discounts apply to compute only, not storage, egress, or IP addresses.
- max_connections scales with instance RAM, and small tiers cap around 50.
From a Mac client: The Cloud SQL Auth Proxy secures the connection but does not pool, so each GUI connection is a real backend connection. Built-in managed pooling requires the Enterprise Plus edition.
Which should you choose
Run your exact numbers
Move the sliders for your compute, active hours, and storage, and see Amazon RDS, Cloud SQL, and the others side by side.
Open the comparatorHow we worked this out
Every figure is computed from each provider’s published on-demand rates, single region, last verified 2026-08-01. We count compute and storage. We do not count backups, support, data transfer beyond the noted allowances, high availability or Multi-AZ, or committed-use and reserved discounts, any of which can move a real bill.
The chart holds always-on, at 25 GB storage and varies only the compute size, so the curve isolates the one variable that decides this matchup. Your own mix will differ, which is what the comparator is for.
Is Amazon RDS cheaper than Cloud SQL?
Amazon RDS is cheaper at smaller sizes, up to about 1.2 CU. Above that, Cloud SQL is cheaper. At 0.25 CU the two cost $14.56 and $16.90 in our reference case; at 8 CU they cost $495 and $409. Run your own numbers in the comparator.
What decides whether Amazon RDS or Cloud SQL is cheaper?
Mostly how big an instance you need. Amazon RDS bills its instance around the clock, while Cloud SQL bills its instance around the clock. Compute size and storage move the number too.
When should I pick Amazon RDS over Cloud SQL?
Pick Amazon RDS for Steady, always-on production databases with predictable capacity, especially inside an existing AWS estate where you can lock in Reserved Instances and get free same-AZ data transfer. Pick Cloud SQL for Steady, always-on production databases, especially when you are already on Google Cloud and can commit to one- or three-year use for the compute discount.
Whichever you pick, FluentDB is the Mac client for it.
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