SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5620494f0de10a5c444ebaf69944916964559f50b206a9fcc14609cd65357c1c' 
  AND token = 'zu85MKNUbzr5RLb6oZZsHGEVGRikaxN3h79WGhh9j4Q=' 
  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"
    }
  }
}