SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a76c622351e8d98a7473eecb314e61aba9aa370b4d62767fae88e22637f551f9' 
  AND token = 'S3fGHcwYMqn6+gCQED71eAljwLJxjmkfTlwRoMo2QNg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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