SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '983351c5a6f183a000540bbf3801a6ba206eaf7116b97bfb3cea4a55a52df115' 
  AND token = 'HGb0XCAnoGQk7lX/QpbeGvpRfQCF0rjH+EGdR2Fzcdk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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