SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '322b8c294fd340c5baee4f83c9c3258bd63349646226076da7771594a764cc56' 
  AND token = 'U3eVD7LihrM+5j+BE0nUyOamgW47RzrV0GRTBGHLkoU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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