SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '936369007257cbde4318ad64de96a2a9202a36ec0243b69f590e4ecff44b1492' 
  AND token = 'LMji8glJB+x3+IVoEHWXgjTv+GT/yjh6vE1wiCbu+Os=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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