SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9d18847fd9cfb2fb16004ea5e9f85f743b611ac573f6610ca3f401cefb56f5a' 
  AND token = 'C1ybtyWg1AVMr59ZNq7pBL/BUxFWhWte5ZKPeq50Lm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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