diff --git a/packages/backend-defaults/config.d.ts b/packages/backend-defaults/config.d.ts
index 1ff45e6679..12da0a7061 100644
--- a/packages/backend-defaults/config.d.ts
+++ b/packages/backend-defaults/config.d.ts
@@ -644,9 +644,9 @@ export interface Config {
              */
             host: string;
             /**
-             * The port number the database is listening on. Defaults to 5432.
+             * The port number the database is listening on.
              */
-            port?: number;
+            port: number;
             /**
              * The database user to authenticate as. This user must have the `rds_iam` role granted.
              */
diff --git a/packages/backend-defaults/src/entrypoints/database/connectors/postgres.test.ts b/packages/backend-defaults/src/entrypoints/database/connectors/postgres.test.ts
index e095a17e11..012b5d9f13 100644
--- a/packages/backend-defaults/src/entrypoints/database/connectors/postgres.test.ts
+++ b/packages/backend-defaults/src/entrypoints/database/connectors/postgres.test.ts
@@ -649,6 +649,7 @@ describe('postgres', () => {
           connection: {
             type: 'rds',
             host: 'mydb.cluster.eu-west-1.rds.amazonaws.com',
+            port: 5432,
             user: 'postgres',
             region: 'eu-west-1',
           },
@@ -662,28 +663,47 @@ describe('postgres', () => {
       expect(conn2.password).toBe('token-2');
     });
 
-    it('defaults port to 5432 for rds connections', async () => {
+    it('returns an expirationChecker that reflects the token TTL', async () => {
       const { Signer } = jest.requireMock('@aws-sdk/rds-signer') as jest.Mocked<
         typeof import('@aws-sdk/rds-signer')
       >;
 
       Signer.prototype.getAuthToken.mockResolvedValue('mock-iam-token');
 
-      await buildPgDatabaseConfig(
+      const configResult = await buildPgDatabaseConfig(
         new ConfigReader({
           client: 'pg',
           connection: {
             type: 'rds',
             host: 'mydb.cluster.eu-west-1.rds.amazonaws.com',
+            port: 5432,
             user: 'postgres',
             region: 'eu-west-1',
           },
         }),
       );
 
-      expect(Signer).toHaveBeenCalledWith(
-        expect.objectContaining({ port: 5432 }),
-      );
+      const conn = await (configResult.connection as () => Promise<any>)();
+
+      expect(conn.expirationChecker).toBeInstanceOf(Function);
+      // Token was just issued, so it should not yet be considered expired.
+      expect(conn.expirationChecker()).toBe(false);
+    });
+
+    it('throws when port is missing for rds connection', async () => {
+      await expect(
+        buildPgDatabaseConfig(
+          new ConfigReader({
+            client: 'pg',
+            connection: {
+              type: 'rds',
+              host: 'mydb.cluster.eu-west-1.rds.amazonaws.com',
+              user: 'postgres',
+              region: 'eu-west-1',
+            },
+          }),
+        ),
+      ).rejects.toThrow(/connection\.port/);
     });
 
     it('falls back to AWS_REGION env var when region is not set in config', async () => {
@@ -703,6 +723,7 @@ describe('postgres', () => {
             connection: {
               type: 'rds',
               host: 'mydb.cluster.us-east-1.rds.amazonaws.com',
+              port: 5432,
               user: 'postgres',
             },
           }),
@@ -727,14 +748,13 @@ describe('postgres', () => {
             client: 'pg',
             connection: {
               type: 'rds',
+              port: 5432,
               user: 'postgres',
               region: 'eu-west-1',
             },
           }),
         ),
-      ).rejects.toThrow(
-        /Missing host in connection config for AWS RDS IAM auth/,
-      );
+      ).rejects.toThrow(/connection\.host/);
     });
 
     it('throws when user is missing for rds connection', async () => {
@@ -745,13 +765,12 @@ describe('postgres', () => {
             connection: {
               type: 'rds',
               host: 'mydb.cluster.eu-west-1.rds.amazonaws.com',
+              port: 5432,
               region: 'eu-west-1',
             },
           }),
         ),
-      ).rejects.toThrow(
-        /Missing user in connection config for AWS RDS IAM auth/,
-      );
+      ).rejects.toThrow(/connection\.user/);
     });
 
     it('throws when region is missing and no env var is set for rds connection', async () => {
@@ -768,6 +787,7 @@ describe('postgres', () => {
               connection: {
                 type: 'rds',
                 host: 'mydb.cluster.eu-west-1.rds.amazonaws.com',
+                port: 5432,
                 user: 'postgres',
               },
             }),
diff --git a/packages/backend-defaults/src/entrypoints/database/connectors/postgres.ts b/packages/backend-defaults/src/entrypoints/database/connectors/postgres.ts
index 53e00e863c..74e95601bd 100644
--- a/packages/backend-defaults/src/entrypoints/database/connectors/postgres.ts
+++ b/packages/backend-defaults/src/entrypoints/database/connectors/postgres.ts
@@ -277,24 +277,21 @@ export async function buildRdsPgConfig(config: Config): Promise<Knex.Config> {
   const { Signer } =
     require('@aws-sdk/rds-signer') as typeof import('@aws-sdk/rds-signer');
 
-  const rawConfig = config.get() as Record<string, unknown>;
-  const normalized = normalizeConnection(rawConfig.connection as any);
-  const sanitizedConnection = omit(normalized, [
-    'type',
-    'region',
-  ]) as Partial<Knex.StaticConnectionConfig>;
-
-  const hostname = (normalized as any).host as string;
-  if (!hostname) {
-    throw new Error('Missing host in connection config for AWS RDS IAM auth');
-  }
-  const port = ((normalized as any).port as number | undefined) ?? 5432;
-  const username = (normalized as any).user as string;
-  if (!username) {
-    throw new Error('Missing user in connection config for AWS RDS IAM auth');
+  let hostname: string;
+  let port: number;
+  let username: string;
+  try {
+    hostname = config.getString('connection.host');
+    port = config.getNumber('connection.port');
+    username = config.getString('connection.user');
+  } catch (err) {
+    throw new ForwardedError(
+      'AWS RDS IAM auth: missing required database connection config — make sure connection.host, connection.port, and connection.user are set and any environment variables they reference are set',
+      err,
+    );
   }
   const region =
-    ((normalized as any).region as string | undefined) ??
+    config.getOptionalString('connection.region') ??
     process.env.AWS_REGION ??
     process.env.AWS_DEFAULT_REGION;
   if (!region) {
@@ -303,17 +300,33 @@ export async function buildRdsPgConfig(config: Config): Promise<Knex.Config> {
     );
   }
 
+  const rawConfig = config.get() as Record<string, unknown>;
+  const sanitizedConnection = omit(
+    config.get('connection') as Record<string, unknown>,
+    ['type', 'region'],
+  ) as Partial<Knex.StaticConnectionConfig>;
+
   const signer = new Signer({ hostname, port, username, region });
 
+  // RDS IAM auth tokens are valid for 15 minutes. Renew 1 minute early so
+  // that pooled connections are refreshed before the token actually expires.
+  const tokenTtlMs = 15 * 60 * 1000;
+  const renewalOffsetMs = 60 * 1000;
+
   async function getConnectionConfig() {
     try {
       const password = await signer.getAuthToken();
-      return { ...sanitizedConnection, password };
+      const tokenExpiration = Date.now() + tokenTtlMs - renewalOffsetMs;
+      return {
+        ...sanitizedConnection,
+        password,
+        expirationChecker: () => tokenExpiration <= Date.now(),
+      };
     } catch (err) {
-      console.error(
-        `AWS RDS IAM auth token acquisition failed for ${username}@${hostname}:${port}: ${err}`,
+      throw new ForwardedError(
+        `AWS RDS IAM auth token acquisition failed for ${username}@${hostname}:${port}`,
+        err,
       );
-      throw err;
     }
   }