SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '59e138138df2f17840255a91d2174c2fb3b7b558e5c4307721b2d3ede588351c' 
  AND token = '0FvKhEK8irB/ikPeDwhqiZHZy2YtxjLLcjKQM3zZyvA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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