SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a600f11eb11ebc51173c3bb4009a1f40e66b4c35b52c46afd5f29ba9ad8d59c9' 
  AND token = 'iLvOTs6eIUS4Cw0c3HtdlxGFqf4esKthdAZZGriyzPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}