I18n translation speed.md

data = {
  foo: 'foo',
  great_grandparent: {
    grandparent: {
      parent: {
        child: {
          foo: 'foo'}
      }
    }
  }
}
I18n.backend.store_translations('en', data)

Benchmark.ips do |b|

  b.time = 1
  
  # auto warmup causes high variability
  b.warmup = 0
  
  # manual warmup to load translations into backend
  I18n.t(:bar)

  b.report("key match (1 lookup)") do
    I18n.t(:foo)
  end

  b.report("fallback to default (2 lookups)") do
    I18n.t(:miss, default: :foo)
  end

  b.report("fallback to default (3 lookups)") do
    I18n.t(:miss, default: [:miss2, :foo])
  end

  b.report("fallback to default (4 lookups)") do
    I18n.t(:miss, default: [:miss2, :miss3, :foo])
  end

  b.report("fallback to default (5 lookups)") do
    I18n.t(:miss, default: [:miss2, :miss3, :miss4, :foo])
  end

  b.report("nested defaults (5 lookups)") do
    I18n.t(:miss, default: [
      :"great_grandparent.grandparent.parent.child.miss",
      :"great_grandparent.grandparent.parent.miss",
      :"great_grandparent.grandparent.miss",
      :"great_grandparent.grandparent.parent.child.foo",
    ])
  end

  b.compare!
end

-------------------------------------------------
key match (1 lookup)     43.244k (±10.5%) i/s -     10.659k
fallback to default (2 lookups)
                         21.227k (±10.7%) i/s -      6.903k
fallback to default (3 lookups)
                         14.405k (±13.2%) i/s -      5.485k in   0.621587s
fallback to default (4 lookups)
                         11.409k (±10.4%) i/s -      4.560k
fallback to default (5 lookups)
                          9.422k (± 9.8%) i/s -      4.084k
nested defaults (5 lookups)
                          8.917k (± 9.7%) i/s -      3.860k in   0.804303s

Comparison:
key match (1 lookup):               43243.6 i/s
fallback to default (2 lookups):    21226.7 i/s - 2.04x slower
fallback to default (3 lookups):    14404.7 i/s - 3.00x slower
fallback to default (4 lookups):    11408.8 i/s - 3.79x slower
fallback to default (5 lookups):     9421.7 i/s - 4.59x slower
nested defaults (5 lookups):         8917.1 i/s - 4.85x slower