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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ad459ddd0a55b4f22ca34a9881db91921299daf2f58a6b65d29c8e15a63e2702' 
  AND token = 'avjcqaV9/aj1aom3+h6DaNoegZKXfr+/Y90NV91sbgc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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