SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3693fe49e7ce3ddfc7a4e198eb1be68e334221071a8ac3df3d9a6c3fb728043' 
  AND token = 'nfTx5/eJ2PqnMa397CXcXoxcmj7HwCvnLUhLOyQUSas=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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