SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '14319add60d20cc7c2a50bb96e898bc4af659563ab7af2516214b289473368ac' 
  AND token = '0mljWRkiNsuUrfAlheTvD9b5h519p6aVCu+LAiBHhHA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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