SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79377ba525be8b090a8300e5609c9b90910dcbb3e93f045daa8f5a60575735db' 
  AND token = 'SAoobv1aPBQfvMuwp69dIaRCVhnbtjdW+wYjbDcHlcs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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