SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a46fd5a843e76403ff3f545b87ed7595fa1907f88f8e2124c86319013ed2ab4c' 
  AND token = '3nxTzLcPIEbhZJlGibkJkdYiPDvCTuWtP+GGpZ8dTL8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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