SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b838a819e3506d57913664da6a616a0bd637af5f251a79eabd9fe7bdaa07e59d' 
  AND token = 'F9Hp2RXKyDGzNIpsMKc6vfGBRmUS2vRpPnH4tILdmK4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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