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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '728eab52cc352f0fa1e4b30d0ca998747b421f1795edcbc8b5a5890a6e748eb4' 
  AND token = 'aJz+TZ3ayHgbOZBxYid/mE4ZCYIzsHeF5mWQOwygtG8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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