SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f730b8d9673a9c28017a0a1e8ad03df73472f747ba78d2b191c841554a66f79d' 
  AND token = '0snEcXy8ZZduzb2rGYJGBvxOBn9VUGMJ0Qp+rH9ENe8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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