SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3dfdb44264e48c0e792e4e863f7f02754abc6584810e54703950d196542a7894' 
  AND token = 'YR1nBIop/YroMcv9LXEjKEFJzpFh4fgXWxZytTHY2Gg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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