PlanetScale Optimized Hostname Routing to the Wrong Region: Direct Hostname Fix

PlanetScale’s optimized hostname can cause queries between a Tokyo-region API and Tokyo-region DB to be routed to Ohio. This article explains the cause based on official documentation and the one-line fix using a direct hostname.

📑Table of Contents

1. PlanetScale Hostname Types and Recommended Use Cases
2. Cause of Cross-Region Routing with Optimized Hostname
3. Steps to Switch to Direct Hostname and Verification
4. Operational Considerations and Alternatives
5. Frequently Asked Questions (FAQ)
6. Summary

What to understand first

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PlanetScale Hostname Types and Recommended Use Cases

PlanetScale provides two main hostname types for connections: optimized hostname and direct hostname.

The optimized hostname uses Route 53 latency-based routing to automatically select the closest edge location for the client. This aims for low latency for globally distributed users. In contrast, the direct hostname connects directly to the Vitess instance in the specified region. It is suitable when you want to avoid cross-region data transfer or need to pin traffic to a specific data center.

Practical check

According to the official documentation (https://planetscale.com/docs/plans/regions), the optimized hostname is the default recommendation, while the direct hostname is intended for scenarios requiring explicit region specification. When operating in the Tokyo region, the choice affects query routing.

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Cause of Cross-Region Routing with Optimized Hostname

Why the route can change

Using the optimized hostname can result in queries from a Tokyo API server to a Tokyo DB being routed across the Pacific to Ohio. This stems from the characteristics of latency-based routing.

Route 53 selects the optimal endpoint based on measured latency from edge locations worldwide. At certain times or under specific network conditions, the Ohio edge may be judged as “closer.” Even for Tokyo-to-Tokyo communication, global optimization can select another region.

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Practical check

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Evidence and comparison

The official documentation (https://planetscale.com/docs/vitess/connecting/network-latency) describes this behavior in the context of network latency for the optimized hostname. The same symptom is also reported in the bookmarked Zenn article (https://zenn.dev/avaintelligence/articles/b7d4743a448485).

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Compare the two routing choices

Hostname Type	Routing Method	Behavior for Tokyo-to-Tokyo	Primary Use Case
optimized	Latency-based routing	May route to other regions (e.g., Ohio)	Global low-latency priority
direct	Direct to specified region	Connects directly to Tokyo DB	Region pinning, avoid cross-region transfer

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Steps to Switch to Direct Hostname and Verification

Switching to the direct hostname requires only changing the host parameter in the connection string.

1. Open the target database in the PlanetScale dashboard and navigate to the “Connect” screen.
2. Locate the “direct hostname” value (typically in the form xxx.ap-northeast-1.psdb.cloud with region specification).
3. Update the application’s connection string (DSN or environment variable) by replacing the host with the direct hostname.
4. Restart or redeploy the application.
5. Verify the correct region in query logs or PlanetScale query insights.

This prevents queries from being routed to Ohio even within the Tokyo region. The change involves only one location in the connection string.

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Operational Considerations and Alternatives

Using the direct hostname may limit automatic failover during regional outages. The optimized hostname improves availability through global routing but can introduce latency variability.

For production environments, validate the direct hostname in a staging environment before adopting it. Another option is implementing a region-aware connection pool on the application side. Regularly review PlanetScale’s official documentation to stay aligned with hostname specification changes.

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Frequently Asked Questions (FAQ)

Q: What is the difference between optimized hostname and direct hostname?

Optimized hostname uses Route 53 latency routing to automatically select the nearest edge. Direct hostname connects directly to the instance in the specified region.

Q: Why does traffic route to Ohio even between Tokyo endpoints?

Latency-based routing determines the global optimum and occasionally selects another region. This can occur depending on network conditions.

Practical check

Q: Is the fix only a single change in the connection string?

Yes. Changing only the host parameter to the direct hostname completes the fix. No other configuration changes are required.

Q: What is the availability impact of using direct hostname?

Automatic failover during regional outages may be limited. Choose based on your operational requirements.

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Summary

Unintended cross-region routing caused by the optimized hostname can be avoided with a one-line change to the connection string. Review the official documentation and consider switching to the direct hostname. Always validate changes in your environment before production deployment.