SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31765fdb621756b018b6129dee8e6c6d0b6a39f7eb555175367f383a260ae7a6' 
  AND token = 'dUFPJ9v7x8NNQZ+/g6lzyr1QcLCTFhN9tRzQLyB56/I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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