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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31db268770eb98ac669583460107d02b758718774ec7b69f569b8bee2cbee033' 
  AND token = '3nimdDMIbpI4ks1T5WLVzBLlVnIfeDqkbYEG9uZmO5o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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