SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '521f145030b4f40ebbeae89bacd08691a0efbd9b0ebb33846a2da19ae54b8d16' 
  AND token = 'JykgXgYYEJUXnSg/gBBBWwOoN+WJ+igCaDP4gnshWI4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}