SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '345f4f2fd45c1fa588459ab9fc3e09738d087cca6b614ff505ed1a97398a7c00' 
  AND token = '+dknK22oOMn24AvLtZUPrAPAZ4bOUC67jZaGUpDQ/zE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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