SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4116be7b99f496954a20a70f2261f168dbc67b20fc43c99079e1e969f8a7318' 
  AND token = 'uU2tKlGGvZpvc/Yt5wDwCyhXIn0A55Ox+gXJ5ghBfDA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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