SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9a8a7d6b4160eca6833410506cd82dfafe2450335660fbd1632ace0c0a931f6d' 
  AND token = 'E6IffcS7e8Bw5D8ajoqhHY/g0AiEQp2UwqkpQMyWQEY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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