SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '66b7ed55902c181b3859808a176666f25756b47afb94e442fe4ee77cba6a0435' 
  AND token = 'nnIeLhXa+jv8YHLEwEWZXyUrMpxwGKHYQ59hueXKA00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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