SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '684532bf7d78b4076d8e8692a1d79379372eb0fe2686a8bcdc20678ff9f08f12' 
  AND token = '4l+g0hgJZxdUsYjaPnLNLQuycT/2gSC+80/K0lDXGd0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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