SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56a7cac18a2fd52e9e81aff293b2af1c3943d1e59983f232b1f6677ade77c853' 
  AND token = '2S7MBC+Y1WK/ujP4IcDr2Uxsq+/dyaukbBXEuWVKHmE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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