SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78f342f1408e076d35fd06ca42c2fc7e207e066a40cdc57602ade754a6a4d599' 
  AND token = 'b/bgFGbE82CqmLy340VtQzuEF5pEebIKnLoLCtUXMj0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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