SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9d42c3828b4f7d622fa1eec4391f2ddaa8591f9ed57d8c712425499eee322a85' 
  AND token = '0v+GjwUk4+kgFKEjtPTdUtGygvffB8WWTuqh9PxXsCY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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