SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '403a34f753ebb9c0933b6e05e6712823ce975d692fd64598db7809574d63f1af' 
  AND token = 'gZNLZ9QRL0cj8EFA22LLUtYMXD0UzG+nbf/BD+/6kJE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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