SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76ba42ab0428ccd85e71cf1af7193a4b912076ccc70cd9e8040338e753c8cbd9' 
  AND token = '2+bCOlCAVmvkn2Worly6Lmk8nxDTeiPR/jyfxBRSzwM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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