SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c63196e0b4a27435e21c878f3a351fe7e5f975e17fe084d12e552e0fb67dfc53' 
  AND token = '40q6/j847dApQTFoncmexpnhtYN7yHPOqEfgCFtEXOs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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