SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81d6d4c791cd9237196e97400e5478360808aa2f4a72b3f46a70583974d6d30f' 
  AND token = '3KLmS7uBnsP5JrXhnZEoUo7hANXjjJeXJ2w1Vrx+CNE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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