SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '627929b2d18bd17406a3e923ba83516bddb35a919478909988c4aaa05d9c0392' 
  AND token = 't+hWHUumqvKRlbaVJ+4mJRPcjSC0crqSwwMA/IZq560=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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