SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '873d88f530ae6a728b139c10ffb63dff314752da057219dd636ede56894fd47e' 
  AND token = 'smxUY4BylQ1lMwHpn06kteSq3T74Fa4RjhhQbMZexCI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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