SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8cd3e91940c374999ded2f69182f2d4818e4f9477fc323f967fffd65664748e' 
  AND token = 'upTUKks/whu7DWpwMyFoQBieww1JmadGCJshyu9tkr0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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