SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8252c638e995ab246f779aeb4d3aa72eddeb9c298b4376f3dbb4d8fb37573df5' 
  AND token = 'g+ojI8hpMtPCo/y+ynaDNG0qMiCZsBvGRnJraUoDuWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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