SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5451a3e10626133ead08d92e6dfd6ac79816497f2642389bfed9feab65484c87' 
  AND token = 'UJ/LLkInUNZyG1UTDxJYZSA8kJvJMAVAOK55JvnkZtY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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