SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56c7881b530aa8953bf191e78b21a65de10f789994f2b2d68ded61df7befc400' 
  AND token = 'bKMOf3VaI3I5JGj5ldyrN2kHy3cpCFu2nIjWXOQVumg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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