diff --git a/lib/fluent/plugin/out_cloudwatch_logs.rb b/lib/fluent/plugin/out_cloudwatch_logs.rb
index ce62913..c103d60 100644
--- a/lib/fluent/plugin/out_cloudwatch_logs.rb
+++ b/lib/fluent/plugin/out_cloudwatch_logs.rb
@@ -162,9 +162,8 @@ def start
       end
       options[:http_proxy] = @http_proxy if @http_proxy
       @logs ||= Aws::CloudWatchLogs::Client.new(options)
-      @sequence_tokens = {}
-      @store_next_sequence_token_mutex = Mutex.new
-
+      @log_groups = {}
+      
       log.debug "Aws::CloudWatchLogs::Client initialized: log.level #{log.level} => #{options[:log_level]}"
 
       @json_handler = case @json_handler
@@ -356,20 +355,6 @@ def scrub_record!(record)
       end
     end
 
-    def delete_sequence_token(group_name, stream_name)
-      @sequence_tokens[group_name].delete(stream_name)
-    end
-
-    def next_sequence_token(group_name, stream_name)
-      @sequence_tokens[group_name][stream_name]
-    end
-
-    def store_next_sequence_token(group_name, stream_name, token)
-      @store_next_sequence_token_mutex.synchronize do
-        @sequence_tokens[group_name][stream_name] = token
-      end
-    end
-
     def put_events_by_chunk(group_name, stream_name, events)
       chunk = []
 
@@ -413,9 +398,6 @@ def put_events(group_name, stream_name, events, events_bytesize)
           log_stream_name: stream_name,
         }
 
-        token = next_sequence_token(group_name, stream_name)
-        args[:sequence_token] = token if token
-
         begin
           t = Time.now
           response = @logs.put_log_events(args)
@@ -424,7 +406,6 @@ def put_events(group_name, stream_name, events, events_bytesize)
             "stream" => stream_name,
             "events_count" => events.size,
             "events_bytesize" => events_bytesize,
-            "sequence_token" => token,
             "thread" => Thread.current.object_id,
             "request_sec" => Time.now - t,
           }
@@ -434,16 +415,6 @@ def put_events(group_name, stream_name, events, events_bytesize)
           else
             log.debug "Called PutLogEvents API", request
           end
-        rescue Aws::CloudWatchLogs::Errors::InvalidSequenceTokenException, Aws::CloudWatchLogs::Errors::DataAlreadyAcceptedException => err
-          sleep 1 # to avoid too many API calls
-          store_next_sequence_token(group_name, stream_name, err.expected_sequence_token)
-          log.warn "updating upload sequence token forcefully because unrecoverable error occured", {
-            "error" => err,
-            "log_group" => group_name,
-            "log_stream" => stream_name,
-            "new_sequence_token" => token,
-          }
-          retry_count += 1
         rescue Aws::CloudWatchLogs::Errors::ResourceNotFoundException => err
           if @auto_create_stream && err.message == 'The specified log stream does not exist.'
             log.warn 'Creating log stream because "The specified log stream does not exist." error is got', {
@@ -452,7 +423,6 @@ def put_events(group_name, stream_name, events, events_bytesize)
               "log_stream" => stream_name,
             }
             create_log_stream(group_name, stream_name)
-            delete_sequence_token(group_name, stream_name)
             retry_count += 1
           else
             raise err
@@ -487,8 +457,6 @@ def put_events(group_name, stream_name, events, events_bytesize)
       if 0 < retry_count
         log.warn "retry succeeded"
       end
-
-      store_next_sequence_token(group_name, stream_name, response.next_sequence_token)
     end
 
     def create_log_group(group_name, log_group_aws_tags = nil, retention_in_days = nil)
@@ -497,7 +465,6 @@ def create_log_group(group_name, log_group_aws_tags = nil, retention_in_days = n
         unless retention_in_days.nil?
           put_retention_policy(group_name, retention_in_days)
         end
-        @sequence_tokens[group_name] = {}
       rescue Aws::CloudWatchLogs::Errors::ResourceAlreadyExistsException
         log.debug "Log group '#{group_name}' already exists"
       end
@@ -517,18 +484,16 @@ def put_retention_policy(group_name, retention_in_days)
     def create_log_stream(group_name, stream_name)
       begin
         @logs.create_log_stream(log_group_name: group_name, log_stream_name: stream_name)
-        @sequence_tokens[group_name] ||= {}
-        @sequence_tokens[group_name][stream_name] = nil
       rescue Aws::CloudWatchLogs::Errors::ResourceAlreadyExistsException
         log.debug "Log stream '#{stream_name}' already exists"
       end
     end
 
     def log_group_exists?(group_name)
-      if @sequence_tokens[group_name]
+      if @log_groups[group_name]
         true
       elsif check_log_group_existence(group_name)
-        @sequence_tokens[group_name] = {}
+        @log_groups[group_name] = []
         true
       else
         false
@@ -547,12 +512,12 @@ def check_log_group_existence(group_name)
     end
 
     def log_stream_exists?(group_name, stream_name)
-      if not @sequence_tokens[group_name]
+      if not @log_groups[group_name]
         false
-      elsif @sequence_tokens[group_name].has_key?(stream_name)
+      elsif @log_groups[group_name].include?(stream_name)
         true
       elsif (log_stream = find_log_stream(group_name, stream_name))
-        @sequence_tokens[group_name][stream_name] = log_stream.upload_sequence_token
+        @log_groups[group_name].push(stream_name)
         true
       else
         false