SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '684dbdc63ecfdbd9a929fc9a18cf946b4052ee1d959956ec37190ba3b1551672' 
  AND token = '2/qO63VzZG0FbL+DVJEu34eHJvVwLc7/qJyLqJiip2M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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