SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '99400b64579481bcba6121e3a814f58af3ceb3a0f4884029f9158fc4598b247c' 
  AND token = '9DsMXcazHcpu24OfYz00fbadlICBFVdvzg85KzcbR2w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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