SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1939ccced3378fdbf93f66cbdc77108e9a08c6f2b16a21bfd7de99b257ad03ba' 
  AND token = 'FDRBeIiQMYZGfOKW14Z4QTsLOxfuLCWJ6J/EVt+GE2I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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