SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4e697f8010b531f120d408995529b56a3348aea761c13321e775f7d178b6f00c' 
  AND token = '0SAJeBvc46O9nhakzZt4UbRmjjKPVrwPEMvJU7dY1xo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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