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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '755d7c43392061a6263daa57a781503f0d94b4addc3b68557399198d2257c5b5' 
  AND token = 'PkcK9byVvF24ypKhbR1nVxK49xWXNOlmtvXHuIpP64o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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