SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '254dc8862ce391a532f697b4446af13d0808d012f9842f903974561145dcc96a' 
  AND token = '7r9XuKItSAHNNIDxyDXQJhl+DLPACKRadmwHYcG/5ws=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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