SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4d8f6276489b275cbdfa0a20abdc3c979e6a90e1f8385436fbedfc90e2d8267' 
  AND token = 'xARRvgCohsyuJdbeIkWBbPjCW+GsHHhpVn95wA1bD8w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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