SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6ca8bd65f089b71754aeb98ee40df9f9abf1e60c3c739d0cb35c81c48031404' 
  AND token = 'PM7Hjk1whpfnjIjTOgXcpYRUVZ/zi+jGCUPToEPRjTI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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