SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5eb40af2e6f20194de298e37c6dce409b6ef0b121cd334743f4369ea2756fc62' 
  AND token = '0TCfrhJc4UIndTAqjXJxEwzy8QCEe9S+HVWnliGe2bc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}