SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '973023b3d9747170e424ab68e0acab908f5e7d1eefa4a8533fc013fbaf7c85b6' 
  AND token = '56jACN+FUJkbugbS/7QI0aeIB2CNV2zyT/OobkSrM04=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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