SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb6b2ebb15e8a2f7da89309aa74d9c9cd88afa20e793987d05be54ec1dfb8eb1' 
  AND token = '37hX1yKiEVm+YFi/ILubGVlvr0HduUJwsGj0JoAPnb8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}