SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '21e291fa9319fb62afe73dd9017928ef500885912c8bc676436c077417d68605' 
  AND token = 'D3LWdUXMMgmjMmiJH2uBDzMnpOe666LXxcgkCm+rxKs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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