SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75793bb21d4fc850378decd15b88df00baadbc5f116f9e7216e7c50aed7cb381' 
  AND token = 'JVwFZgPc101AODMXALcgyuIhGnB+lSjEMBJceTKuFLA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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