SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '139b6ae4040fe36a26e46536ebcf80e592345080c6954129e9ce4288f77f716d' 
  AND token = 'swULeuiis42OcxDWBrCBA/ixH11dnwlqidEGIpaB/lo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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