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What Is a POOL Record?

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What is a POOL record?

A POOL record is a record type developed by DNSimple for basic traffic distribution. It randomly distributes incoming requests across multiple target hostnames, acting as a lightweight, DNS-based load balancer for your services. POOL records are part of DNS hosting at DNSimple and are available on certain plans.

While standard CNAME records can alias one name to another, they lack the ability to dynamically choose between several destinations. The POOL record solves this by enabling you to define a collection (pool) of hostnames that a single CNAME-like record can point to, randomly selecting one at resolution time.

How POOL records work: CNAME resolution with random selection

The selection happens on DNSimple’s authoritative name servers.

When a DNS resolver queries a domain name with a configured POOL record:

  1. DNSimple’s name server randomly selects one of the target hostnames defined within your POOL record.
  2. It returns this randomly chosen hostname to the requesting resolver as if it were a standard CNAME record.
  3. The resolver looks up the IP address of that chosen hostname, directing the user’s traffic to one of your specified providers.

This dynamic selection process occurs with each new resolution request, allowing you to randomly distribute incoming traffic across all active members of your pool.

Key benefits and use cases for POOL records

POOL records offer several significant advantages for managing your online services.

Simple load distribution

Ideal for distributing traffic across multiple instances of an application, multiple content delivery network (CDN) providers, or different cloud service endpoints. This helps balance the load and improve responsiveness.

Maintenance and manual failover

  • Graceful removal: You can easily remove a specific provider or server from the pool at any time. Once removed, and after DNS caches have expired, no new requests are directed to that provider, so you can do maintenance or decommission it without downtime.
  • Basic failover: While not a full health-check system, you can remove unhealthy endpoints to manually steer traffic away from issues.

A/B testing (basic)

For simple scenarios, you could use a POOL record to randomly send users to different versions of a site or service to observe behavior.

Vendor redundancy

Distribute traffic across different service providers (e.g., example.provider1.com, example.provider2.com), reducing reliance on a single vendor.

Warning

POOL records are a proprietary record type created by DNSimple. They are resolved and managed exclusively by DNSimple’s name servers. If your domain’s DNS is not hosted with DNSimple, or if you transfer it to another provider, POOL records will not function.

Managing POOL records in DNSimple

You add POOL records, and add or remove target hostnames, in your domain’s record editor. For the record format, see POOL Record Reference.

Have more questions?

If you have additional questions or need any assistance with your POOL records, just contact support, and we will be happy to help.