Part of discussion at https://github.com/pydantic/pydantic/discussions/6388

pydantic_validate_json.py

import json
import random
import uuid
from datetime import date
import timeit
from typing import TypeVar, Generic

import pydantic_core

from pydantic import BaseModel


class PModel(BaseModel):
    field1: str
    field2: str
    field3: int | None = None
    field4: int | None = None
    field5: int | None = None
    field6: int | None = None
    field7: int | None = None
    field8: uuid.UUID | None = None
    field9: uuid.UUID | None = None
    field10: bool | None = None
    field11: int | None = None
    field12: str | None = None
    field13: str | None = None
    field14: bool | None = None
    # field15: IdModel
    id: str
    uuid: uuid.UUID
    field16: str | None = None
    field17: float | None = None
    field18: date | None = None


P = TypeVar('P')


class Result(BaseModel, Generic[P]):
    id: int
    uuid: uuid.UUID
    properties: P


class Response(BaseModel, Generic[P]):
    results: list[Result[P]]


# debug(Response[PModel].__pydantic_core_schema__)


def rand_str():
    return ''.join(random.choice('abcdefghijklmnopqrstuvwxyz') for i in range(random.randint(1, 10)))


def rand_num():
    return random.randint(1, 1_000)


def gen_p():
    return {
        'field1': rand_str(),
        'field2': rand_str(),
        'field3': rand_num(),
        # skip half of the optional fields
        'field5': rand_num(),
        'field7': rand_num(),
        'field9': str(uuid.uuid4()),
        'field10': True,
        'field12': rand_str(),
        'field14': False,
        'id': rand_str(),
        'uuid': str(uuid.uuid4()),
    }


def gen_result():
    return {
        'id': rand_num(),
        'uuid': str(uuid.uuid4()),
        'properties': gen_p(),
    }


def gen_response():
    return {'results': [gen_result() for _ in range(1000)]}


json_data = json.dumps(gen_response()).encode()

timer = timeit.Timer(
    'Response[PModel].model_validate_json(json_data)',
    globals={'Response': Response, 'PModel': PModel, 'json_data': json_data},
)
n, t = timer.autorange()
print(f'model_validate_json(...): {t / n * 1_000:.2f}ms')

timer = timeit.Timer(
    'Response[PModel].model_validate(json.loads(json_data))',
    globals={'Response': Response, 'PModel': PModel, 'json_data': json_data, 'json': json},
)
n, t = timer.autorange()
print(f'model_validate(json.loads(...)): {t / n * 1_000:.2f}ms')

timer = timeit.Timer('json.loads(json_data)', globals={'json_data': json_data, 'json': json})
n, t = timer.autorange()
print(f'json.loads(...): {t / n * 1_000:.2f}ms')

timer = timeit.Timer(
    'pydantic_core.from_json(json_data)', globals={'json_data': json_data, 'pydantic_core': pydantic_core}
)
n, t = timer.autorange()
print(f'pydantic_core.from_json(...): {t / n * 1_000:.2f}ms')