SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '300b8bd028e0ead401b85bb84f3fb20964f35ba2e541541ee84a2249ed75a581' 
  AND token = 'Yc3XMbbVC/K76UA+tMcwRpyLgTqu+93nR9WF/AL4F6U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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