SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6dc46d80ef95dd18343df31f259345570e9ecf5453a7a8a0f2784465646f0db2' 
  AND token = 'KX755xXdNTSMQFBjiBnsawIhhXzAbFoxxKdwUUzZaSo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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