SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6af706eef4fa5ff553f48764e2ab137d7faf011d11088394709973a16651f55b' 
  AND token = 'DB4HecXlpZwsg1ZCvxMWjXDB/sHGGnghY4O39D3y4ws=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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