SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7409a2536f48f1643b52f41189a9d47f7e1fcf2d2b2718c70c0cff492c63721' 
  AND token = 'rUoR536qnrZavhgQoWfcbkgNXCsxGwDd+dtOgO7SnCs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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