SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '814ad8e2adf414129300c0876c862c8de04db348bcead5943c8366cbcf71ecac' 
  AND token = 'zs70YrfnlwItjPKNJQuWh9TBp03j6esu/p+eYD9FnqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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