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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f3bf7dcddf59f3fde319c256c5c4cb890e8c1dfc75e5eed47db4dee8c6f6968' 
  AND token = 'F51Btk2SfIqoTzoZzLEbco/yWHXVRfWoNXfqmZSz9x8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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