SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50475c4a7ba71c868eae7c3f1137f6115848d35bc8d52fa9bc3df024eb210084' 
  AND token = 'JXD5JwNFmhMP5UuVFhC8zdVthDQP4zUmpL3tkC4EpdY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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