SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5d4c3dcf27438efe5ec3a0da932188450e14e3039c4af56785bf43029532aee' 
  AND token = 'MxCqwva+vV+DcdMQtGJyFDLFNN63MKXsx2aMviOxAh4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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