SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4c57d279e79ec1c553bb0dd23cf575f4a7138e5cf73a7299eec39fff72aec49' 
  AND token = '9DHhUYbEBwpDtjVvZNN3nNUc754zExaDzXGdX+t+g+E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}