SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9876f771fb3718757cf5796db884847489cc39d303f101518aff6334b38a73e6' 
  AND token = '3auaJDzHnmlmwPVpl7zMRVs9I1pGJvAss8QQbllO1mc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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