SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '836ec78488d24cbfd94d7e777f728279a68b745652986b95f22c0e86657db46e' 
  AND token = 'TmGwyYQDci8UZmqVvoZHt+cQGCmPc87n9RzKmnGuKnI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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