SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7e28535c0e851a3ac5bffbc813a34a55e981cb24b6f2f2e32231e271e348b277' 
  AND token = '4SYYus68uSvZWykzfsbQipBtBM2yVycXo1O5Gc2Y/cY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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