StackExchange.Redis 3.3 Moves Off a Redis Node Before the Server Drops You

StackExchange.Redis 3.3.0 shipped on September 18, 2026, followed by 3.3.1 on September 22. The headline feature is server-native maintenance notifications, which other Redis clients call “smart client handoffs” or “hitless upgrades”. Redis Enterprise and Redis Cloud can now warn the .NET client that a shard is migrating, a node is failing over, or the endpoint it is connected to is about to be replaced, and the client acts on it instead of waiting for a socket to die.

If you have ever seen a burst of RedisTimeoutException during a managed Redis maintenance window, this is the fix for that class of problem.

What the client does with each notification

The notifications arrive as RESP3 push frames on the same connection that carries your commands. Per the design notes in PR #3191, the client reacts without any code from you:

• MIGRATING, FAILING_OVER, SMIGRATING: command timeouts on that server are relaxed (10 seconds by default, maintRelaxedTimeout).
• MIGRATED, FAILED_OVER: the window closes, with a short relaxed tail while things settle.
• SMIGRATED: the cluster topology is re-read and sharded subscriptions whose slots moved are re-subscribed.
• MOVING: the client asks for the replacement address, drains in-flight work, and swaps the connection before the server closes it.

That last one matters most. The author measured DNS trailing a MOVING notification by 4 to 19 seconds, while the server closes the old socket at roughly 16 to 19 seconds. By asking the server to name the replacement endpoint (maintMovingEndpointType=Auto, the default), the handoff becomes a direct move that completes within a second.

Turning it on in 3.3

It is opt-in for now, even when you connect to a recognized Redis Cloud or Azure Managed Redis hostname. The documentation says auto-enlistment for those providers is planned for a follow-up release. The connection string route is the simplest:

var muxer = await ConnectionMultiplexer.ConnectAsync(
    "my-redis.example.com:6379,maintNotifications=Auto,maintRelaxedTimeout=15");

The strongly typed API is marked experimental, and in 3.3.1 that is a compile error, not a warning:

error SER010: 'StackExchange.Redis.ConfigurationOptions.MaintenanceNotifications' is for
evaluation purposes only and is subject to change or removal in future updates.

Suppress it explicitly if you want the property and the event types:

#pragma warning disable SER010
using StackExchange.Redis;
using StackExchange.Redis.Maintenance;

var options = ConfigurationOptions.Parse("my-redis.example.com:6379");
options.MaintenanceNotifications = MaintenanceNotificationMode.Auto;

var muxer = await ConnectionMultiplexer.ConnectAsync(options);
muxer.ServerMaintenanceEvent += (_, e) =>
{
    if (e is PushMaintenanceEvent m)
        Console.WriteLine($"{m.NotificationType} seq {m.SequenceId} from {m.EndPoint}");
};

MaintenanceNotificationMode has three values. Disabled is the current default. Auto asks during the handshake and carries on if the server refuses. Enabled rejects the connection if notifications cannot be delivered, including when the connection lands on RESP2, which makes it a useful way to prove the feature is live in staging.

Two things to check before you ship it

RESP3 is required. protocol=resp2, a defaultVersion below 6.0, or disabling HELLO in the command map all silently turn the feature off under Auto.

A deliberate handoff also shows up as a ConnectionFailed event with FailureType == ConnectionFailureType.MaintenanceHandoff. If you alert on ConnectionFailed, filter that value out or your pager goes off during every planned maintenance.

One change is not opt-in: 3.3.0 adds topologyRefreshSeconds, which re-reads the topology every 30 minutes by default (jittered, 0 disables it). It exists for endpoints that still answer a handshake but no longer belong to the deployment.

If Redis already sits behind your HybridCache, see how to use HybridCache in ASP.NET Core 11 with Redis as the L2 cache. Adding maintNotifications=Auto to that connection string is the cheapest resilience upgrade you will make this month.