SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '140ef702a960ea092d153f1287f2a04270fb72983ee1afb22956cbad4b26e57e' 
  AND token = '15/iTmFs5OdvsrN8jMRmZYvJej9OACdBTek1QuxguTA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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