perf: query used columns only and avoid to use limit

app/models/lock_script.rb

@@ -32,7 +32,7 @@ def lock_info
         block_interval = (epoch_number * 1800 + since_value_index * 1800 / since_value.length) - (tip_epoch.number * 1800 + tip_epoch.index * 1800 / tip_epoch.length)
 
         if block_interval.negative?
-          block = Block.where(epoch: since_value.number).recent.first
+          block = Block.where(epoch: since_value.number).order(number: :desc).select(:start_number, :length)[0]
           new_index = since_value_index < block.length ? since_value_index : since_value_index * block.length / since_value.length
           block_timestamp = Block.where(number: block.start_number + new_index).pick(:timestamp)
           estimated_unlock_time = DateTime.strptime(block_timestamp.to_s, "%Q")