SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a8846b9ca0aba56fda20106134016c3ee92ed934d089da7b7fd860510f8ee7f' 
  AND token = 'WGoj7ppwl7gl2Hzv72JQ7y2XIsKDGEgVMCkk7jf1zTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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