SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51fc48b47d72ae6899d2286f09d7693d0625ac179cc2f11acb5b7098aa169e64' 
  AND token = 'PtMfjtDwNboncjBL8690/vaMXMVPQe2o1ejZVZrp8zg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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