SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f78248fc7fef5ed9c818d56afee48920d494c110bd76ffde9ed1a555ea6b939' 
  AND token = 'l0IfOmzieXrNzg5134sg4vxmlHEuNdsGoTNAdObxGWU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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