SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb8d59d95c7720efbfaf56def5920c60efbea04360ace2dc69c9299e0f246c3b' 
  AND token = 'ZxVnEhuwZ867wz+PFagYkzSlv7NgswxjwBjpQBnIQFU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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