SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '393142ff03b100ed659885cd34f2d57b12915ef89f1b602063318d465472124c' 
  AND token = 'b/WsqC515ZyxT4nIYMem85I3+j2btsIC7/d5FPNdiRo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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