SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2c2762e791f1330159576e1e8551e0e383dd60a8d2ccda3c50c8e89c7799f52' 
  AND token = '6mWlxkGzIUatBfqRPRV92amUmEBjqcyqRJEByJwUQZU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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