SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a517272fd3c112387723b913442faf2209c8b5aa6481a515f1ed6c7323dac3d6' 
  AND token = 'HMnAdTcrTJBVuSPLKJhQtFtV9+9cV26c7TAh4+kc/u4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}