SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '834a7455b9d9b42337ec67856fc3687e1aba8d417fac553bc593856b87a04d84' 
  AND token = 'zE5dKuQjsvZj7RTyPrW7dB4bdP83CnJwbuGIu9SJ6Nc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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