AWS RDS for PostgreSQL vs MongoDB Atlas
Neither wins outright: AWS RDS for PostgreSQL is cheaper for 2 of 3 workloads and MongoDB Atlas for the rest.
List prices checked
Rate cards side by side
Only the axes at least one of them bills on. A dash means that provider does not charge for it.
| Billing axis | AWS RDS for PostgreSQL | MongoDB Atlas | Difference |
|---|---|---|---|
| Entry plan | $12.40/mo | $9.00/mo | 1.4× MongoDB Atlas |
| Storage | $0.115/GB-mo | $0.250/GB-mo | 2.2× AWS RDS for PostgreSQL |
| Free tier | Yes | Yes | — |
Source: Amazon Web Services pricing (May 2026) · MongoDB pricing (May 2026). Published list prices only — committed-use discounts, regional variation, and per-request charges are not included. Not yet independently re-checked against the vendor’s page.
Monthly cost for three real workloads
The rate cards applied to identical usage. This is where the winner changes.
| Workload | AWS RDS for PostgreSQL | MongoDB Atlas | Cheaper |
|---|---|---|---|
| Side projectA personal site or small app with modest traffic, a few gigabytes of assets, and one small always-on process. | $15 | $14 | MongoDB Atlassaves $0.70/mo (5%) |
| Growing SaaSA funded product serving a few thousand daily users, with an image-heavy frontend and two application servers. | $70 | $134 | AWS RDS for PostgreSQLsaves $64/mo (48%) |
| Media-heavy siteA publisher or video product where delivery dominates the bill and compute is almost an afterthought. | $242 | $509 | AWS RDS for PostgreSQLsaves $267/mo (52%) |
Workload definitions are identical on every comparison page, so figures here can be read against any other pair in the same category.
What each one is for
AWS RDS for PostgreSQL
by Amazon Web Services
Provisioned Postgres billed per instance-hour whether or not it serves a query, plus storage and backup. Predictable, and the most expensive way to run an idle database.
Free tier: 750 hours per month of a db.t-class instance for 12 months
MongoDB Atlas
by MongoDB
The managed service from MongoDB itself, with a permanently free shared tier and dedicated clusters priced per instance size across three clouds.
Free tier: M0 shared cluster with 512 MB, always free
Common questions
- Is AWS RDS for PostgreSQL or MongoDB Atlas cheaper in 2026?
- It depends on volume — AWS RDS for PostgreSQL wins 2 of the 3 modelled workloads and MongoDB Atlas wins 1. The scenario table above shows where the crossover falls.
- Which has the better free tier, AWS RDS for PostgreSQL or MongoDB Atlas?
- Both publish one. AWS RDS for PostgreSQL: 750 hours per month of a db.t-class instance for 12 months. MongoDB Atlas: M0 shared cluster with 512 MB, always free.
- What do these estimates not include?
- Committed-use and reserved discounts, regional price variation, per-request API charges, support plans, and minimum retention periods. All of those move real invoices, sometimes by a lot. These figures compare published list prices for the same workload, which is the comparison the rate cards alone cannot give you.