SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57c29918ccd03bb6437dd312a03648cb2bd7127978ae1f1a1f3b899c74cddfc2' 
  AND token = '5GqsCzwqoblTJ+ZxwB4jwV+iql8QLFUlaGZxIjkRrgM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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