SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '338c4671de03036fdf492547b51b44972990a3dcf2cf5a83d334b492f85f240f' 
  AND token = 'HGStFcjrr5MXNlUDzZITjVKyftAuxpphYHPcgA43ZxI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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