SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3ce7dbfa5cc2be4516486fd217ac4df1e7ff108d8c07d674f8610f3238b0f873' 
  AND token = '0iz4jDU3kwpaJfK/Tt42UoRVxKPAFBWxYOEJihZq5Lg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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