SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '538add8066241271bb470dc4a1274579ebf7c021b5c0678ab68857d52e7ae0fb' 
  AND token = '6e3ensad1R/HRyQPNlikpBHlb2+HOQQSt6ya4bF5MlE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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