SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8923f46016e126779a086d16a7a939dca918312d127d1f288893e5e064691fa0' 
  AND token = 'VcOwK0EhgYXnuBGaph4xxMhWSDKRg7IDXjIvc6p7nDc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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