SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84a6bbef39126c386980b45980cd7762aed42ed38e9a6e374c7ddd15548ca460' 
  AND token = '/vT38Mh5rb0Zi4nKiYwVNdfHhcl9rOT0AC4wNPQlXCg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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