SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c77acaa796312bc89ce300fdb8b934af997256b429ddada64008e44bf7815a73' 
  AND token = 'rK9nKPQG47Jofkkw76BnLYx+nwVVV9zx/7PT5T4RSQg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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