SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8a5833c407bddfb047fb6666554204edc54fcb918136714efd3e7a6a4834a02' 
  AND token = 'vR+ObLEPTcHhiEqgU2/HTN5SD+ivRTUMr9ijMX/zJCU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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