SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '429606aeaa9d8b039b7154ed2d21adfee18923a1e375cc37350592c8ec26f768' 
  AND token = 'ExaMIH0cByc/JoqSzZ/Y7MZtWWUVTeoAmkAOiYkcv0s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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