SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76f61fda238133a17267401b3046238eaa8f8f858d5f0882fa28d2a3b34dca7d' 
  AND token = 'dya0mI7Ex3XVPQ/GhbszqArYS+hNRyvsTUUI2JrLGi8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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