SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21785cac7dae466d486515809694d42cbdfa6550e432f302cebc805f793819e1' 
  AND token = 'sMoUH2773PCjgOUmPAyAlmDfYx4jnV324BbKCwoKk5Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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