SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '85affbeaf9a62d2ac517a924783ff63d20e069a7b5a04340a0ebbfd2dbae90d4' 
  AND token = 'LFTFZUuVJwKB7vHHCSioZKm2/7xZBgBQgtCj4bvg5aU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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