SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8976ee3825ca76672be599b2b91a48e3173d64a106b1c758e0dcddd998804783' 
  AND token = '5N25givUMj7ltEZiEjgNOhUSnJUqU8t0KVsE49MSJrY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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