SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b0487df08e5ab8848b820b69ac3c766c82244a0d5b8b13444eb42fa621a4435' 
  AND token = '5sVrVbgYhrTwgLUEGRSYkAKESzjjhnSTluCWkc1wMKk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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