SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f9a0dea9d0fe56710ac8fbf90eb78927278641cdd6baf271fbc333d01657346' 
  AND token = '5jEd8rXJi9LNYjTFcSD9QBdOF8g0NKSve4a25CUwLJg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00070

JSON explain

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