SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68ee57a4b80dec3ffad280385108f7029401222e8005b83244538a98210af893' 
  AND token = 'ebJTUI6nbafoZ1S1YnWgMzWC9A4A/SFjaxzlkmT+7zs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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