SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e2661345217924020da0804c6bec736906011c612a860550dd7b432dfbc91e50' 
  AND token = 'LTiHga/c9yV/KQhV0oj5Bs5Tpw2FqqHj+YSb3uJmqPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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