SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8e2ce85f5901214aabf5b244fe404c07bc1e7120669606d5488330fd69da369' 
  AND token = 'A/+gba+tZpajqlDf+cpFUIFoH2RVwHBRd3oUpN1muqk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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