SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '38bdfad80bec9085f21fa656eb8ad8701e065f15fee6142f665cffe825026488' 
  AND token = 'R7wxZRRmj+/7VIyOcwtJMq06vaHcrPVUCPUnCn1OOd8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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