SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ab4e72c4fd19489d09fb29bd71af0f1f364dff828662d68c7ec4323426d99313' 
  AND token = 'nTvCILnZItYHCefYEEe4ekW2vmrU2IwovWIea066Tw0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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