SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fdf303706e0a5d14f5a6e464ad0af9cb07947d2c30f66b1a854d971ea8d16a8' 
  AND token = 'U4UIpKBdLC1mlDmg1+nf9Xz9D9nowqKn6nNo4lPn4kA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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