SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6121c80b9ead16287b0ab2a99ed9ef6f16fb85d80ba9a27a0c5be49f49ea31b9' 
  AND token = '69OqhiO2lZYQUsZPd8Kbv+n4QTkJ7MYycYvoMRGPlR8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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