diff --git a/.gitignore b/.gitignore
index 932fae0..2a815a9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,3 +12,4 @@
 
 *.iml
 .idea
+/vendor
diff --git a/.ruby-version b/.ruby-version
index 818bd47..fa7adc7 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.0.6
+3.3.5
diff --git a/lib/avromatic/model/raw_serialization.rb b/lib/avromatic/model/raw_serialization.rb
index 395902f..dd4fbe8 100644
--- a/lib/avromatic/model/raw_serialization.rb
+++ b/lib/avromatic/model/raw_serialization.rb
@@ -15,8 +15,10 @@ module Encode
 
         UNSPECIFIED = Object.new
 
+        # rubocop:disable Style/AccessModifierDeclarations
         delegate :datum_writer, :datum_reader, to: :class
         private :datum_writer, :datum_reader
+        # rubocop:enable Style/AccessModifierDeclarations
 
         def avro_raw_value(validate: UNSPECIFIED)
           unless validate == UNSPECIFIED
diff --git a/lib/avromatic/model/types/abstract_type.rb b/lib/avromatic/model/types/abstract_type.rb
index 7b85a5d..7ef9ef3 100644
--- a/lib/avromatic/model/types/abstract_type.rb
+++ b/lib/avromatic/model/types/abstract_type.rb
@@ -4,6 +4,7 @@ module Avromatic
   module Model
     module Types
       class AbstractType
+
         EMPTY_ARRAY = [].freeze
         private_constant :EMPTY_ARRAY
 
@@ -23,12 +24,12 @@ def coerce(_input)
           raise "#{__method__} must be overridden by #{self.class.name}"
         end
 
-        def coercible?(_input)
-          raise "#{__method__} must be overridden by #{self.class.name}"
+        def coercible?(input)
+          input.nil? || input_classes.any? { |input_class| input.is_a?(input_class) }
         end
 
-        def coerced?(_value)
-          raise "#{__method__} must be overridden by #{self.class.name}"
+        def coerced?(value)
+          value.nil? || value_classes.any? { |value_class| value.is_a?(value_class) }
         end
 
         # Note we use positional args rather than keyword args to reduce
diff --git a/lib/avromatic/model/types/array_type.rb b/lib/avromatic/model/types/array_type.rb
index 8394db9..c322a20 100644
--- a/lib/avromatic/model/types/array_type.rb
+++ b/lib/avromatic/model/types/array_type.rb
@@ -38,7 +38,7 @@ def coercible?(input)
         end
 
         def coerced?(value)
-          value.nil? || (value.is_a?(::Array) && value.all? { |element| value_type.coerced?(element) })
+          value.nil? || (value.is_a?(::Array) && value.all? { |element_input| value_type.coerced?(element_input) })
         end
 
         def serialize(value, strict)
diff --git a/lib/avromatic/model/types/big_int_type.rb b/lib/avromatic/model/types/big_int_type.rb
new file mode 100644
index 0000000..bea1046
--- /dev/null
+++ b/lib/avromatic/model/types/big_int_type.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require 'avromatic/model/types/abstract_type'
+
+module Avromatic
+  module Model
+    module Types
+      class BigIntType < AbstractType
+        VALUE_CLASSES = [::Integer].freeze
+
+        MAX_RANGE = 2**63
+
+        def self.in_range?(value)
+          value.is_a?(::Integer) && value.between?(-MAX_RANGE, MAX_RANGE - 1)
+        end
+
+        def value_classes
+          VALUE_CLASSES
+        end
+
+        def name
+          'bigint'
+        end
+
+        def coerce(input)
+          if coercible?(input)
+            input
+          else
+            raise ArgumentError.new("Could not coerce '#{input.inspect}' to #{name}")
+          end
+        end
+
+        def coercible?(input)
+          input.nil? || self.class.in_range?(input)
+        end
+
+        alias_method :coerced?, :coercible?
+
+        def serialize(value, _strict)
+          value
+        end
+
+        def referenced_model_classes
+          EMPTY_ARRAY
+        end
+      end
+    end
+  end
+end
diff --git a/lib/avromatic/model/types/boolean_type.rb b/lib/avromatic/model/types/boolean_type.rb
index 3022f03..2988efd 100644
--- a/lib/avromatic/model/types/boolean_type.rb
+++ b/lib/avromatic/model/types/boolean_type.rb
@@ -24,12 +24,6 @@ def coerce(input)
           end
         end
 
-        def coercible?(input)
-          input.nil? || input.is_a?(::TrueClass) || input.is_a?(::FalseClass)
-        end
-
-        alias_method :coerced?, :coercible?
-
         def serialize(value, _strict)
           value
         end
diff --git a/lib/avromatic/model/types/date_type.rb b/lib/avromatic/model/types/date_type.rb
index e296863..a9dfdbf 100644
--- a/lib/avromatic/model/types/date_type.rb
+++ b/lib/avromatic/model/types/date_type.rb
@@ -7,11 +7,16 @@ module Model
     module Types
       class DateType < AbstractType
         VALUE_CLASSES = [::Date].freeze
+        INPUT_CLASSES = [::Date, ::Time].freeze
 
         def value_classes
           VALUE_CLASSES
         end
 
+        def input_classes
+          INPUT_CLASSES
+        end
+
         def name
           'date'
         end
@@ -26,12 +31,6 @@ def coerce(input)
           end
         end
 
-        def coercible?(input)
-          input.nil? || input.is_a?(::Date) || input.is_a?(::Time)
-        end
-
-        alias_method :coerced?, :coercible?
-
         def serialize(value, _strict)
           value
         end
diff --git a/lib/avromatic/model/types/decimal_type.rb b/lib/avromatic/model/types/decimal_type.rb
index 0218b0f..89cacbf 100644
--- a/lib/avromatic/model/types/decimal_type.rb
+++ b/lib/avromatic/model/types/decimal_type.rb
@@ -42,14 +42,6 @@ def coerce(input)
           end
         end
 
-        def coercible?(input)
-          input.nil? || input_classes.any? { |input_class| input.is_a?(input_class) }
-        end
-
-        def coerced?(value)
-          value.nil? || value_classes.any? { |value_class| value.is_a?(value_class) }
-        end
-
         def serialize(value, _strict)
           value
         end
diff --git a/lib/avromatic/model/types/enum_type.rb b/lib/avromatic/model/types/enum_type.rb
index 5521678..248c79b 100644
--- a/lib/avromatic/model/types/enum_type.rb
+++ b/lib/avromatic/model/types/enum_type.rb
@@ -38,8 +38,8 @@ def coerce(input)
           end
         end
 
-        def coerced?(input)
-          input.nil? || (input.is_a?(::String) && allowed_values.include?(input))
+        def coerced?(value)
+          value.nil? || value.is_a?(::String) && allowed_values.include?(value)
         end
 
         def coercible?(input)
diff --git a/lib/avromatic/model/types/float_type.rb b/lib/avromatic/model/types/float_type.rb
index 6d6d257..76128e7 100644
--- a/lib/avromatic/model/types/float_type.rb
+++ b/lib/avromatic/model/types/float_type.rb
@@ -31,14 +31,6 @@ def coerce(input)
           end
         end
 
-        def coercible?(input)
-          input.nil? || input.is_a?(::Float) || input.is_a?(::Integer)
-        end
-
-        def coerced?(input)
-          input.nil? || input.is_a?(::Float)
-        end
-
         def serialize(value, _strict)
           value
         end
diff --git a/lib/avromatic/model/types/integer_type.rb b/lib/avromatic/model/types/integer_type.rb
index 66365e1..92177e3 100644
--- a/lib/avromatic/model/types/integer_type.rb
+++ b/lib/avromatic/model/types/integer_type.rb
@@ -8,6 +8,12 @@ module Types
       class IntegerType < AbstractType
         VALUE_CLASSES = [::Integer].freeze
 
+        MAX_RANGE = 2**31
+
+        def self.in_range?(value)
+          value.is_a?(::Integer) && value.between?(-MAX_RANGE, MAX_RANGE - 1)
+        end
+
         def value_classes
           VALUE_CLASSES
         end
@@ -17,7 +23,7 @@ def name
         end
 
         def coerce(input)
-          if input.nil? || input.is_a?(::Integer)
+          if coercible?(input)
             input
           else
             raise ArgumentError.new("Could not coerce '#{input.inspect}' to #{name}")
@@ -25,7 +31,7 @@ def coerce(input)
         end
 
         def coercible?(input)
-          input.nil? || input.is_a?(::Integer)
+          input.nil? || self.class.in_range?(input)
         end
 
         alias_method :coerced?, :coercible?
diff --git a/lib/avromatic/model/types/record_type.rb b/lib/avromatic/model/types/record_type.rb
index 82a9a79..44b5027 100644
--- a/lib/avromatic/model/types/record_type.rb
+++ b/lib/avromatic/model/types/record_type.rb
@@ -36,10 +36,6 @@ def coercible?(input)
           false
         end
 
-        def coerced?(value)
-          value.nil? || value.is_a?(record_class)
-        end
-
         def serialize(value, strict)
           if value.nil?
             value
diff --git a/lib/avromatic/model/types/string_type.rb b/lib/avromatic/model/types/string_type.rb
index 954c18d..0e5d585 100644
--- a/lib/avromatic/model/types/string_type.rb
+++ b/lib/avromatic/model/types/string_type.rb
@@ -31,14 +31,6 @@ def coerce(input)
           end
         end
 
-        def coercible?(input)
-          input.nil? || input.is_a?(::String) || input.is_a?(::Symbol)
-        end
-
-        def coerced?(value)
-          value.nil? || value.is_a?(::String)
-        end
-
         def serialize(value, _strict)
           value
         end
diff --git a/lib/avromatic/model/types/type_factory.rb b/lib/avromatic/model/types/type_factory.rb
index c6eae95..0fe4c12 100644
--- a/lib/avromatic/model/types/type_factory.rb
+++ b/lib/avromatic/model/types/type_factory.rb
@@ -9,6 +9,7 @@
 require 'avromatic/model/types/fixed_type'
 require 'avromatic/model/types/float_type'
 require 'avromatic/model/types/integer_type'
+require 'avromatic/model/types/big_int_type'
 require 'avromatic/model/types/map_type'
 require 'avromatic/model/types/null_type'
 require 'avromatic/model/types/record_type'
@@ -31,7 +32,7 @@ module TypeFactory
           'bytes' => Avromatic::Model::Types::StringType.new,
           'boolean' => Avromatic::Model::Types::BooleanType.new,
           'int' => Avromatic::Model::Types::IntegerType.new,
-          'long' => Avromatic::Model::Types::IntegerType.new,
+          'long' => Avromatic::Model::Types::BigIntType.new,
           'float' => Avromatic::Model::Types::FloatType.new,
           'double' => Avromatic::Model::Types::FloatType.new,
           'null' => Avromatic::Model::Types::NullType.new
diff --git a/lib/avromatic/model/types/union_type.rb b/lib/avromatic/model/types/union_type.rb
index e2661a1..721b734 100644
--- a/lib/avromatic/model/types/union_type.rb
+++ b/lib/avromatic/model/types/union_type.rb
@@ -76,7 +76,15 @@ def referenced_model_classes
         private
 
         def find_index(value)
-          # TODO: Cache this?
+          if value.is_a?(::Integer)
+            if Avromatic::Model::Types::IntegerType.in_range?(value)
+              return member_types.index { |member_type| member_type.is_a?(Avromatic::Model::Types::IntegerType) }
+            elsif Avromatic::Model::Types::BigIntType.in_range?(value)
+              return member_types.index { |member_type| member_type.is_a?(Avromatic::Model::Types::BigIntType) }
+            end
+          end
+
+          # TODO: Consider caching the index for each value class
           member_types.find_index do |member_type|
             member_type.value_classes.any? { |value_class| value.is_a?(value_class) }
           end
diff --git a/spec/avro/dsl/test/real_int_union.rb b/spec/avro/dsl/test/real_int_union.rb
new file mode 100644
index 0000000..1f22815
--- /dev/null
+++ b/spec/avro/dsl/test/real_int_union.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+namespace :test
+
+record :real_int_union do
+  required :header, :string
+  required :message, :union, types: [:int, :string, :long]
+end
diff --git a/spec/avro/schema/test/logical_types.avsc b/spec/avro/schema/test/logical_types.avsc
index e17fca8..22d8d5d 100644
--- a/spec/avro/schema/test/logical_types.avsc
+++ b/spec/avro/schema/test/logical_types.avsc
@@ -24,6 +24,15 @@
         "logicalType": "timestamp-micros"
       }
     },
+    {
+      "name": "decimal",
+      "type": {
+        "type": "bytes",
+        "logicalType": "decimal",
+        "precision": 4,
+        "scale": 2
+      }
+    },
     {
       "name": "unknown",
       "type": {
diff --git a/spec/avro/schema/test/real_int_union.avsc b/spec/avro/schema/test/real_int_union.avsc
new file mode 100644
index 0000000..9c32a7e
--- /dev/null
+++ b/spec/avro/schema/test/real_int_union.avsc
@@ -0,0 +1,19 @@
+{
+  "type": "record",
+  "name": "real_int_union",
+  "namespace": "test",
+  "fields": [
+    {
+      "name": "header",
+      "type": "string"
+    },
+    {
+      "name": "message",
+      "type": [
+        "int",
+        "string",
+        "long"
+      ]
+    }
+  ]
+}
diff --git a/spec/avromatic/io/datum_reader_spec.rb b/spec/avromatic/io/datum_reader_spec.rb
index 1aa30b5..64df092 100644
--- a/spec/avromatic/io/datum_reader_spec.rb
+++ b/spec/avromatic/io/datum_reader_spec.rb
@@ -44,7 +44,7 @@
         b: '123',
         tf: true,
         i: rand(10),
-        l: 123456789,
+        l: 2**40,
         f: 0.5,
         d: 1.0 / 3.0,
         n: nil,
diff --git a/spec/avromatic/io/datum_writer_spec.rb b/spec/avromatic/io/datum_writer_spec.rb
index 237bce7..d9f6f3a 100644
--- a/spec/avromatic/io/datum_writer_spec.rb
+++ b/spec/avromatic/io/datum_writer_spec.rb
@@ -52,4 +52,55 @@
       end
     end
   end
+
+  context "with int/bigint union" do
+    let(:schema_name) { 'test.real_int_union' }
+
+    context "for int" do
+      let(:values) do
+        {
+          header: 'foo',
+          message: 1
+        }
+      end
+
+      describe "#write_union" do
+        before { datum_writer.write_union(union_schema, datum, encoder) }
+
+        context "when the datum includes union member index" do
+          it "does not call Avro::Schema.validate" do
+            expect(Avro::Schema).not_to have_received(:validate)
+          end
+
+          it "calls write_data to encode the union" do
+            expect(datum_writer).to have_received(:write_data).with(union_schema.schemas[0], datum.datum, encoder)
+          end
+        end
+      end
+    end
+
+    context "for big int" do
+      let(:values) do
+        {
+          header: 'foo',
+          message: 1587961247350867973
+        }
+      end
+
+      describe "#write_union" do
+        before { datum_writer.write_union(union_schema, datum, encoder) }
+
+        context "when the datum includes union member index" do
+          it "does not call Avro::Schema.validate" do
+            expect(Avro::Schema).not_to have_received(:validate)
+          end
+
+          it "calls write_data to encode the union" do
+            expect(datum_writer).to have_received(:write_data).with(union_schema.schemas[2], datum.datum, encoder)
+          end
+        end
+      end
+    end
+  end
+
 end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index ed3c416..5c76535 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -19,7 +19,7 @@
 
   config.before do
     Avromatic.logger = Logger.new('log/test.log')
-    Avromatic.registry_url = 'http://username:password@registry.example.com'
+    Avromatic.registry_url = 'http://username:password@registry.localhost'
     Avromatic.use_schema_fingerprint_lookup = true
     Avromatic.schema_store = AvroTurf::SchemaStore.new(path: 'spec/avro/schema')
     Avromatic.custom_type_registry.clear