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AWS RDS Proxy

What it is

Amazon RDS Proxy is a fully-managed, highly available proxy layer for Amazon RDS and Amazon Aurora databases. It speaks the MySQL / Postgres wire protocol on both sides — applications connect to RDS Proxy as if it were the database — and provides two production-critical functions as a paid add-on service:

  1. Connection pooling. RDS Proxy multiplexes a large number of short-lived client connections onto a smaller pool of long-lived backend connections to the writer and reader endpoints, reducing per-connection CPU / memory burn on the underlying compute nodes. Each MySQL / Postgres connection consumes backend resources; pooling amortises that cost.

  2. Fast failover. On writer-node failure RDS Proxy "can also more quickly detect the outage and redirect traffic to another node without dropping client connections" — a meaningful improvement over client- driven endpoint re-resolution + reconnect on Aurora's in-built failover. (Source: sources/2024-02-15-planetscale-amazon-aurora-pricing-surprising-costs)

Why it shows up on this wiki

RDS Proxy is the canonical wiki instance of connection pooling as a paid add-on in the managed-database category — distinct from the bundled-pooling choice PlanetScale makes with vtgate (MySQL/Vitess) or PgBouncer inside the proprietary proxy (Postgres). Whether a DB product bundles pooling or charges for it as an add-on is a structural differentiator that directly shapes operator cost + complexity: concepts/connection-pooling-cost-axis.

Cost shape

"This is an additional service on top of Aurora and thus incurs an additional charge on your AWS bill." (Source: sources/2024-02-15-planetscale-amazon-aurora-pricing-surprising-costs) RDS Proxy is priced per vCPU-hour of the underlying RDS instance it fronts; customers who enable it pay for the proxy fleet separately from the compute + storage bill of the database itself.

Contrast with Vitess vtgate

PlanetScale's functional equivalent — canonical patterns/vtgate-as-rds-proxy-equivalent:

"A component of all MySQL clusters managed by Vitess is known as vtgate, a lightweight proxy that routes traffic to the correct MySQL node in the cluster. This component is similar to RDS Proxy in that it speaks the MySQL protocol and manages all of the connections to the MySQL nodes, reducing the resources utilized by each node… Since vtgate is a core component of Vitess, PlanetScale can support a nearly unlimited number of connections and it is included in the cost of running a PlanetScale database."

vtgate is both a sharding router and a pooler; PlanetScale's product positioning bundles both behind one bill. RDS Proxy is pooling-plus-failover without sharding — Aurora's per-cluster storage handles the scale-out that vtgate does via shard routing.

Contrast with PgBouncer-inside-proprietary-proxy

On the Postgres side the equivalent shape is PgBouncer bundled inside PlanetScale for Postgres's proprietary proxy. The structural difference is the same — paid add-on vs bundled, and the bundled version can layer query-buffering + automatic- failover integration that standalone PgBouncer doesn't provide.

Seen in

  • sources/2024-02-15-planetscale-amazon-aurora-pricing-surprising-costs — canonical disclosure of RDS Proxy's dual role (connection pooling + fast failover) as a paid add-on service on top of Aurora / RDS. Used by Morrison as the contrast point for PlanetScale's bundled-vtgate + bundled-PgBouncer story. First canonical wiki instance of RDS Proxy.
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