SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '785a4e18ca118ed4a15893aa7be2f2bdd65a01a5159da82a8290089e224d5bc3' 
  AND token = 'u36DTvlXdgkA1himZYhVGlufxP0WRYjF9iwjYwSH9Cs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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