SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57c50c955f6e72505c1ad000988aa69ea432b2727fd23f2a34d92018c3cf8b51' 
  AND token = 'c2fzU/2f/9YppMnIpcuCNkotQdA4kwNURRQR/zCkmr0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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