diff --git a/code/hash/symbol-vs-string-keys-building.rb b/code/hash/symbol-vs-string-keys-building.rb
new file mode 100644
index 0000000..58f47f8
--- /dev/null
+++ b/code/hash/symbol-vs-string-keys-building.rb
@@ -0,0 +1,31 @@
+require 'benchmark/ips'
+
+# The same 1000 keys, as Symbols, frozen Strings and plain Strings, each mapped to its index.
+SYMBOL_KEYS = (1..1000).map { |i| :"key_#{i}" }
+FROZEN_KEYS = (1..1000).map { |i| "key_#{i}".freeze }
+STRING_KEYS = (1..1000).map { |i| "key_#{i}" }
+
+def build(keys)
+  keys.each_with_index.map { |key, index| [key, index] }.to_h
+end
+
+# Symbol and frozen String keys tie on Ruby 4.0.
+def faster
+  build(SYMBOL_KEYS)
+end
+
+# A Hash copies and freezes a plain String key, but keeps a frozen one as it is.
+def fast
+  build(FROZEN_KEYS)
+end
+
+def slow
+  build(STRING_KEYS)
+end
+
+Benchmark.ips do |x|
+  x.report('Symbol Keys') { faster }
+  x.report('Frozen Keys') { fast }
+  x.report('String Keys') { slow }
+  x.compare!
+end
diff --git a/code/hash/symbol-vs-string-keys-reading.rb b/code/hash/symbol-vs-string-keys-reading.rb
new file mode 100644
index 0000000..8d776ea
--- /dev/null
+++ b/code/hash/symbol-vs-string-keys-reading.rb
@@ -0,0 +1,30 @@
+require 'benchmark/ips'
+
+# The same 1000 keys, as Symbols, frozen Strings and plain Strings, each mapped to its index.
+SYMBOL_KEYS = (1..1000).map { |i| :"key_#{i}" }
+FROZEN_KEYS = (1..1000).map { |i| "key_#{i}".freeze }
+STRING_KEYS = (1..1000).map { |i| "key_#{i}" }
+
+SYMBOL_HASH = SYMBOL_KEYS.each_with_index.map { |key, index| [key, index] }.to_h
+FROZEN_HASH = FROZEN_KEYS.each_with_index.map { |key, index| [key, index] }.to_h
+STRING_HASH = STRING_KEYS.each_with_index.map { |key, index| [key, index] }.to_h
+
+# Reads every key once.
+def faster
+  SYMBOL_KEYS.each { |key| SYMBOL_HASH[key] }
+end
+
+def fast
+  FROZEN_KEYS.each { |key| FROZEN_HASH[key] }
+end
+
+def slow
+  STRING_KEYS.each { |key| STRING_HASH[key] }
+end
+
+Benchmark.ips do |x|
+  x.report('Symbol Keys') { faster }
+  x.report('Frozen Keys') { fast }
+  x.report('String Keys') { slow }
+  x.compare!
+end