SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '946d598f084df77255d23cdfcb34689e2eb9dec257b97ac8e8a98e62919b268d' 
  AND token = '6EuEPqRuZXlpsCIRmFZ8fgxKt+UIYimuhSIBR6/FalA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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