SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6bf342b698948b406667338ffe56234a19695f3095d2fa7c6524b7962fc5c97' 
  AND token = 'pfBWoZ+W8gewIm6YFGmzgpjXsTE+GN5xwRy33/HOaXQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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