String vs Symbol instantiation. When possible, prefer symbols, as they have on average half the instantiation time.

string-symbol

[9] pry(main)> n = 1_000
=> 1000
[10] pry(main)> Benchmark.bm { |bm|
[10] pry(main)*   bm.report { n.times { :foo }}
[10] pry(main)*   bm.report { n.times { 'foo'}}
[10] pry(main)* }  
       user     system      total        real
   0.000000   0.000000   0.000000 (  0.000192)
   0.000000   0.000000   0.000000 (  0.000396)
=> [#<Benchmark::Tms:0x0000000263dfd8
  @cstime=0.0,
  @cutime=0.0,
  @label="",
  @real=0.000192456,
  @stime=0.0,
  @total=0.0,
  @utime=0.0>,
 #<Benchmark::Tms:0x000000026a6880
  @cstime=0.0,
  @cutime=0.0,
  @label="",
  @real=0.000395832,
  @stime=0.0,
  @total=0.0,
  @utime=0.0>]