SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7dd4f68b923d25571d468ff00177a57613fd5d1467a856d79f2afd888fde3c19' 
  AND token = '8+Br2z00EPEX9k2LdxWzCH9o2twd75/JswuvnaPkMjg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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