SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81942da5ecdedf02b441d4f8eaf896260a343854a8a6a55cfe9f7114532c24c2' 
  AND token = 'Kgl7Ve3KewzrzLcgfmUkKqVTplzaB9iCeZPdtt2qgGY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}