SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '89ff7b76a199791d7f226c274faec8faf6bf9536181316e6afa9f895e86db576' 
  AND token = '1z1JHwKiCdIBDrO6WiWCTjFCWRW6fw8gUoi+sxOOeYw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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