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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a921561f94fca3bdadf3f841ad6cdb3bb7f862acf28296ff915e5efdbbc4ab15' 
  AND token = 'Ru4NB+9qNazR2vHgQEE+bkfdUKmLMbKco/PvNjTaXnA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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