SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '708f56319478357dcdc72fca2f5c5785c7de312854362a39fff6110cff8d0cb3' 
  AND token = 'Di0qXa3nAs5mrQmC05EggN9G8+bOAzsPiFjpYT5bIDM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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