SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a876c9353e0ee9f0dbb6d838b00ea366854fbb24974e29a421f8ffebda29926a' 
  AND token = 'z76Gu9yiuKoD2rMXtpa9iT/sM+gKVUiZzOJow3bhJGE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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