diff --git a/src/scalar/json.ts b/src/scalar/json.ts
index 5a23504..4a941de 100644
--- a/src/scalar/json.ts
+++ b/src/scalar/json.ts
@@ -12,9 +12,9 @@ const validate = (value: string) => {
   }
 };
 
-class JSONType implements Scalar<string> {
+class JSONType implements Scalar<Uint8Array> {
   private _valid = false;
-  private _value = '';
+  private _value = new TextEncoder().encode(NULL_VALUE);
 
   public constructor(v?: unknown) {
     this.value = v;
@@ -29,7 +29,7 @@ class JSONType implements Scalar<string> {
     return this._valid;
   }
 
-  public get value(): string {
+  public get value(): Uint8Array {
     return this._value;
   }
 
@@ -40,14 +40,14 @@ class JSONType implements Scalar<string> {
     }
 
     if (typeof value === 'string') {
-      this._value = value;
+      this._value = new TextEncoder().encode(value);
       this._valid = validate(value);
       return;
     }
 
     if (value instanceof Uint8Array) {
-      this._value = new TextDecoder().decode(value);
-      this._valid = validate(this._value);
+      this._value = value;
+      this._valid = validate(new TextDecoder().decode(value));
       return;
     }
 
@@ -58,7 +58,7 @@ class JSONType implements Scalar<string> {
     }
 
     try {
-      this._value = JSON.stringify(value);
+      this._value = new TextEncoder().encode(JSON.stringify(value));
       this._valid = true;
     } catch {
       throw new Error(`Unable to set '${value}' as JSON`);
@@ -67,7 +67,7 @@ class JSONType implements Scalar<string> {
 
   public toString() {
     if (this._valid) {
-      return this._value;
+      return new TextDecoder().decode(this._value);
     }
 
     return NULL_VALUE;
diff --git a/src/scalar/uuid.ts b/src/scalar/uuid.ts
index 41a1db2..e87d008 100644
--- a/src/scalar/uuid.ts
+++ b/src/scalar/uuid.ts
@@ -1,27 +1,26 @@
-import { Utf8 as ArrowString } from '@apache-arrow/esnext-esm';
+import { FixedSizeBinary } from '@apache-arrow/esnext-esm';
 import { validate } from 'uuid';
 
 import { Scalar } from './scalar.js';
 import { isInvalid, NULL_VALUE } from './util.js';
 
-export class UUID implements Scalar<string> {
+export class UUID implements Scalar<Uint8Array> {
   private _valid = false;
-  private _value = '';
+  private _value = new TextEncoder().encode(NULL_VALUE);
 
   public constructor(v?: unknown) {
     this.value = v;
-    return this;
   }
 
   public get dataType() {
-    return new ArrowString();
+    return new FixedSizeBinary(16);
   }
 
   public get valid(): boolean {
     return this._valid;
   }
 
-  public get value(): string {
+  public get value(): Uint8Array {
     return this._value;
   }
 
@@ -32,14 +31,14 @@ export class UUID implements Scalar<string> {
     }
 
     if (typeof value === 'string') {
-      this._value = value;
+      this._value = new TextEncoder().encode(value);
       this._valid = validate(value);
       return;
     }
 
     if (value instanceof Uint8Array) {
-      this._value = new TextDecoder().decode(value);
-      this._valid = validate(this._value);
+      this._value = value;
+      this._valid = validate(new TextDecoder().decode(value));
       return;
     }
 
@@ -50,8 +49,8 @@ export class UUID implements Scalar<string> {
     }
 
     if (typeof value!.toString === 'function' && value!.toString !== Object.prototype.toString) {
-      this._value = value!.toString();
-      this._valid = validate(this._value);
+      this._value = Buffer.from(value!.toString());
+      this._valid = validate(value!.toString());
       return;
     }
 
@@ -60,7 +59,7 @@ export class UUID implements Scalar<string> {
 
   public toString() {
     if (this._valid) {
-      return this._value;
+      return new TextDecoder().decode(this._value);
     }
 
     return NULL_VALUE;
diff --git a/src/scheduler/cqid.test.ts b/src/scheduler/cqid.test.ts
index bd7f778..44bae2c 100644
--- a/src/scheduler/cqid.test.ts
+++ b/src/scheduler/cqid.test.ts
@@ -27,8 +27,9 @@ test('setCQId - should set to random value if deterministicCQId is false', (t):
 
   setCQId(resource, false, () => NIL_UUID);
 
-  t.is(resource.getColumnData(cqIDColumn.name).valid, true);
-  t.is(resource.getColumnData(cqIDColumn.name).value.toString(), NIL_UUID);
+  const cqId = resource.getColumnData(cqIDColumn.name);
+  t.is(cqId.valid, true);
+  t.is(cqId.toString(), NIL_UUID);
 });
 
 test('setCQId - should set to random value if deterministicCQId is true and table does not have non _cq_id PKs', (t): void => {
@@ -50,8 +51,9 @@ test('setCQId - should set to random value if deterministicCQId is true and tabl
 
   setCQId(resource, true, () => NIL_UUID);
 
-  t.is(resource.getColumnData(cqIDColumn.name).valid, true);
-  t.is(resource.getColumnData(cqIDColumn.name).value.toString(), NIL_UUID);
+  const cqId = resource.getColumnData(cqIDColumn.name);
+  t.is(cqId.valid, true);
+  t.is(cqId.toString(), NIL_UUID);
 });
 
 test('setCQId - should set to fixed value if deterministicCQId is true and table has non _cq_id PKs', (t): void => {
@@ -78,6 +80,7 @@ test('setCQId - should set to fixed value if deterministicCQId is true and table
 
   setCQId(resource, true);
 
-  t.is(resource.getColumnData(cqIDColumn.name).valid, true);
-  t.is(resource.getColumnData(cqIDColumn.name).value.toString(), '415bd5dd-9bac-5806-b9d1-c53f17d37455');
+  const cqId = resource.getColumnData(cqIDColumn.name);
+  t.is(cqId.valid, true);
+  t.is(cqId.toString(), '415bd5dd-9bac-5806-b9d1-c53f17d37455');
 });
diff --git a/src/schema/arrow.ts b/src/schema/arrow.ts
index 1c63e23..d27d8d6 100644
--- a/src/schema/arrow.ts
+++ b/src/schema/arrow.ts
@@ -9,3 +9,6 @@ export const METADATA_TABLE_NAME = 'cq:table_name';
 export const METADATA_TABLE_TITLE = 'cq:table_title';
 export const METADATA_TABLE_DESCRIPTION = 'cq:table_description';
 export const METADATA_TABLE_DEPENDS_ON = 'cq:table_depends_on';
+
+export const METADATA_ARROW_EXTENSION_NAME = 'ARROW:extension:name';
+export const METADATA_ARROW_EXTENSION_METADATA = 'ARROW:extension:metadata';
diff --git a/src/schema/column.ts b/src/schema/column.ts
index 4225c66..186944d 100644
--- a/src/schema/column.ts
+++ b/src/schema/column.ts
@@ -2,6 +2,8 @@ import { isDeepStrictEqual } from 'node:util';
 
 import { DataType, Field, Utf8 } from '@apache-arrow/esnext-esm';
 
+import { ExtensionType, isExtensionType } from '../types/extensions.js';
+
 import * as arrow from './arrow.js';
 import { ClientMeta } from './meta.js';
 import { Resource } from './resource.js';
@@ -60,7 +62,13 @@ export const toArrowField = (column: Column): Field => {
   metadataMap.set(arrow.METADATA_UNIQUE, unique ? arrow.METADATA_TRUE : arrow.METADATA_FALSE);
   metadataMap.set(arrow.METADATA_INCREMENTAL, incrementalKey ? arrow.METADATA_TRUE : arrow.METADATA_FALSE);
 
-  return new Field(name, type, /*nullable=*/ !notNull, metadataMap);
+  if (isExtensionType(type)) {
+    const { name, metadata } = type as unknown as ExtensionType;
+    metadataMap.set(arrow.METADATA_ARROW_EXTENSION_NAME, name);
+    metadataMap.set(arrow.METADATA_ARROW_EXTENSION_METADATA, metadata);
+  }
+
+  return new Field(name, type, !notNull, metadataMap);
 };
 
 export const fromArrowField = (field: Field): Column => {
diff --git a/src/schema/meta.test.ts b/src/schema/meta.test.ts
index 08afbfa..71c6267 100644
--- a/src/schema/meta.test.ts
+++ b/src/schema/meta.test.ts
@@ -95,6 +95,7 @@ test('parentCqUUIDResolver - should set to _cq_id column value when parent has i
 
   parentCqUUIDResolver()({ id: () => '' }, childResource, cqParentIDColumn);
 
-  t.is(childResource.getColumnData(cqParentIDColumn.name).value, '9241a9cb-f580-420f-8fd7-46d2c4f55ccb');
-  t.is(childResource.getColumnData(cqParentIDColumn.name).valid, true);
+  const cqParentId = childResource.getColumnData(cqParentIDColumn.name);
+  t.is(cqParentId.valid, true);
+  t.is(cqParentId.toString(), '9241a9cb-f580-420f-8fd7-46d2c4f55ccb');
 });
diff --git a/src/schema/resource.ts b/src/schema/resource.ts
index 3d70f02..5c90a84 100644
--- a/src/schema/resource.ts
+++ b/src/schema/resource.ts
@@ -1,6 +1,7 @@
 import { tableToIPC, Table as ArrowTable, RecordBatch, vectorFromArray } from '@apache-arrow/esnext-esm';
 
 import { Scalar, Vector, newScalar, Stringable } from '../scalar/scalar.js';
+import { isExtensionType } from '../types/extensions.js';
 
 import { cqIDColumn } from './meta.js';
 import { Table, toArrowSchema } from './table.js';
@@ -59,7 +60,11 @@ export const encodeResource = (resource: Resource): Uint8Array => {
   let batch = new RecordBatch(schema, undefined);
   for (let index = 0; index < table.columns.length; index++) {
     const column = table.columns[index];
-    const data = resource.getColumnData(column.name);
+    // For extension types, we need to get the underlying value
+    const data = isExtensionType(column.type)
+      ? resource.getColumnData(column.name).value
+      : resource.getColumnData(column.name);
+
     const vector = vectorFromArray([data], column.type);
     batch = batch.setChildAt(index, vector);
   }
diff --git a/src/types/extensions.ts b/src/types/extensions.ts
new file mode 100644
index 0000000..8e032ed
--- /dev/null
+++ b/src/types/extensions.ts
@@ -0,0 +1,13 @@
+import { DataType } from '@apache-arrow/esnext-esm';
+
+import { JSONType } from './json.js';
+import { UUIDType } from './uuid.js';
+
+export interface ExtensionType {
+  get name(): string;
+  get metadata(): string;
+}
+
+const extensions = [JSONType, UUIDType];
+
+export const isExtensionType = (type: DataType) => extensions.some((extension) => type instanceof extension);
diff --git a/src/types/json.ts b/src/types/json.ts
index ab0cb4e..5396ac5 100644
--- a/src/types/json.ts
+++ b/src/types/json.ts
@@ -1,13 +1,16 @@
-import { DataType, Type } from '@apache-arrow/esnext-esm';
+import { Type, DataType } from '@apache-arrow/esnext-esm';
 
-export class JSONType extends DataType<Type.Utf8> {
-  readonly extensionName: string = 'json';
+import { ExtensionType } from './extensions.js';
 
-  constructor() {
-    super();
+export class JSONType extends DataType<Type.Binary> implements ExtensionType {
+  get name(): string {
+    return 'json';
+  }
+  get metadata(): string {
+    return 'json-serialized';
   }
 
-  get typeId(): Type.Utf8 {
-    return Type.Utf8;
+  get typeId(): Type.Binary {
+    return Type.Binary;
   }
 }
diff --git a/src/types/uuid.ts b/src/types/uuid.ts
index d0ee013..ef7133e 100644
--- a/src/types/uuid.ts
+++ b/src/types/uuid.ts
@@ -1,23 +1,20 @@
-import { DataType, Type } from '@apache-arrow/esnext-esm';
+import { Type, FixedSizeBinary } from '@apache-arrow/esnext-esm';
 
-export class UUIDType extends DataType<Type.Utf8> {
-  readonly extensionName: string = 'uuid';
+import { ExtensionType } from './extensions.js';
 
+export class UUIDType extends FixedSizeBinary implements ExtensionType {
   constructor() {
-    super();
+    super(16);
   }
 
-  get typeId(): Type.Utf8 {
-    return Type.Utf8;
+  get name(): string {
+    return 'uuid';
   }
-
-  public toString() {
-    return `uuid`;
+  get metadata(): string {
+    return 'uuid-serialized';
   }
 
-  protected static [Symbol.toStringTag] = ((proto: UUIDType) => {
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    (<any>proto).ArrayType = Uint8Array;
-    return (proto[Symbol.toStringTag] = 'uuid');
-  })(UUIDType.prototype);
+  get typeId(): Type.FixedSizeBinary {
+    return Type.FixedSizeBinary;
+  }
 }