AWS SDK Version 3 for .NET
API Reference

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Finds new players to fill open slots in currently running game sessions. The backfill match process is essentially identical to the process of forming new matches. Backfill requests use the same matchmaker that was used to make the original match, and they provide matchmaking data for all players currently in the game session. FlexMatch uses this information to select new players so that backfilled match continues to meet the original match requirements.

When using FlexMatch with Amazon GameLift managed hosting, you can request a backfill match from a client service by calling this operation with a GameSessions ID. You also have the option of making backfill requests directly from your game server. In response to a request, FlexMatch creates player sessions for the new players, updates the GameSession resource, and sends updated matchmaking data to the game server. You can request a backfill match at any point after a game session is started. Each game session can have only one active backfill request at a time; a subsequent request automatically replaces the earlier request.

When using FlexMatch as a standalone component, request a backfill match by calling this operation without a game session identifier. As with newly formed matches, matchmaking results are returned in a matchmaking event so that your game can update the game session that is being backfilled.

To request a backfill match, specify a unique ticket ID, the original matchmaking configuration, and matchmaking data for all current players in the game session being backfilled. Optionally, specify the GameSession ARN. If successful, a match backfill ticket is created and returned with status set to QUEUED. Track the status of backfill tickets using the same method for tracking tickets for new matches.

Only game sessions created by FlexMatch are supported for match backfill.

Learn more

Backfill existing games with FlexMatch

Matchmaking events (reference)

How Amazon GameLift FlexMatch works


This is an asynchronous operation using the standard naming convention for .NET 4.5 or higher. For .NET 3.5 the operation is implemented as a pair of methods using the standard naming convention of BeginStartMatchBackfill and EndStartMatchBackfill.

Namespace: Amazon.GameLift
Assembly: AWSSDK.GameLift.dll
Version: 3.x.y.z


public abstract Task<StartMatchBackfillResponse> StartMatchBackfillAsync(
         StartMatchBackfillRequest request,
         CancellationToken cancellationToken


Type: Amazon.GameLift.Model.StartMatchBackfillRequest

Container for the necessary parameters to execute the StartMatchBackfill service method.

Type: System.Threading.CancellationToken

A cancellation token that can be used by other objects or threads to receive notice of cancellation.

Return Value

The response from the StartMatchBackfill service method, as returned by GameLift.


InternalServiceException The service encountered an unrecoverable internal failure while processing the request. Clients can retry such requests immediately or after a waiting period.
InvalidRequestException One or more parameter values in the request are invalid. Correct the invalid parameter values before retrying.
NotFoundException THe requested resources was not found. The resource was either not created yet or deleted.
UnsupportedRegionException The requested operation is not supported in the Region specified.

Version Information

.NET Core App:
Supported in: 3.1

.NET Standard:
Supported in: 2.0

.NET Framework:
Supported in: 4.5

See Also