SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd5b4bfe03a273633285aecc4d005bc4adc5e703b1afc809bf507327cb43f4044' 
  AND token = 'duBlzFj2lXPWjeb7stiHVlx+bZQiG4k5qxveRueLi08=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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