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func (r *sessionRepository) PreserveSession(sessionId, userId string) error {
	key := fmt.Sprintf("SESSION#%s", sessionId)

	input := &dynamodb.TransactWriteItemsInput{
		TransactItems: []types.TransactWriteItem{
			{
				Update: &types.Update{
					TableName: aws.String(r.tableName),
					Key: map[string]types.AttributeValue{
						"pk": &types.AttributeValueMemberS{Value: key},
						"sk": &types.AttributeValueMemberS{Value: key},
					},
					UpdateExpression: aws.String(
						"SET #current = #current + :incr",
					),
					ExpressionAttributeNames: map[string]string{
						"#current":   "current",
						"#pk":        "pk",
						"#headcount": "headcount",
					},
					ExpressionAttributeValues: map[string]types.AttributeValue{
						":incr": &types.AttributeValueMemberN{
							Value: "1",
						},
					},
					ConditionExpression: aws.String(
						"attribute_exists(#pk) AND #current < #headcount",
					),
				},
			},
			{
				ConditionCheck: &types.ConditionCheck{
					TableName: aws.String(r.tableName),
					Key: map[string]types.AttributeValue{
						"pk": &types.AttributeValueMemberS{Value: fmt.Sprintf("USER#%s", userId)},
						"sk": &types.AttributeValueMemberS{Value: key},
					},
					ConditionExpression: aws.String(
						"attribute_not_exists(pk) AND attribute_not_exists(sk)",
					),
				},
			},
		},
	}

	_, err := r.client.TransactWriteItems(context.TODO(), input)
	if err != nil {
		slog.Error("err/preserve-session", "error", err)
		var ccf *types.TransactionCanceledException
		if errors.As(err, &ccf) {
			return protocol.NewError(protocol.DATA_INTEGRITY_ERROR, "Integrity error")
		}
		return err
	}

	return nil
}