SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b54c10252b1fb2409df72b55ddd22021446b3fae2668474748195bace36e42ba' 
  AND token = 'KA1l/CBLHZh4hXZRjI3zp4PzZ+fIh0GwWDRL/gr2GZk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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