SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e456ff26472aea4d15fe24e8d323496fbe18b0cc9f53a787d7e1ebb83e5608' 
  AND token = '1LvRd/Rp4q+Z6hCinMGHDYlFY3zCSgxElqF5p6+mw/4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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