SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71cf0d3614b30af832e99042fdc30faa609abf93e1c72331066d7b4885118c81' 
  AND token = 'oBxC0QsHKSB9G74KskptaXBBYGY70aMNZRusnSlBPPE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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