SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15279ca65ecc36ec489739bbe7e50cbf484f35e05979b58d50768844d0aef839' 
  AND token = 'g0Y/n9sw/Kc5fBfnpfV65lh+JL+XwSYOnJoIgrNlJHs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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