SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e5903fd1531092445861d775b70882f918b7960ce4dfd533a7a5f07d0aa06c7' 
  AND token = '2EhNj/MOq86psnXAjKFc4lHp2/CeC+IbPN7gLVPSU6s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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