SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7d98aa6c8c3a02fd78ed2c5cc16dbf721a87766894436d30811d479187608542' 
  AND token = '6rMaXkdaXTzxbUvwwPXEk2OiSJilRjPZl7NNxJS7erY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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