What's the correct way to use inDatabase: within an async networking call?

Posting data

- (void) sendPostData:(NSDictionary *)data withDbIndexArray:(NSMutableArray *)dbIndexArray {
    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
    manager.requestSerializer = [AFJSONRequestSerializer serializer];
    
    [manager POST:[_urlEndpoint absoluteString] parameters:data success:^(AFHTTPRequestOperation *operation, id responseObject) {
        NSLog(@"JSON: %@", responseObject);
        [_dbQueue inDatabase:^(FMDatabase *db) {
            for (int i=0; i < dbIndexArray.count; i++) {
                NSLog(@"Removing event at index: %@", dbIndexArray[i]);
                [_db removeEventWithId:[[dbIndexArray objectAtIndex:i] longLongValue]];
                [dbIndexArray removeObjectAtIndex:i];
            }
        }];
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        NSLog(@"Error: %@", error);
        //Add event to queue
    }];
    //    [dbIndexArray removeAllObjects];

}

// SO: http://stackoverflow.com/questions/24719913/whats-the-correct-way-to-use-indatabase-within-an-async-networking-call