SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6696bf4d2579c83d9888efbd5e27640a79b24c65dcc922db6aee9e660e671a8a' 
  AND token = 'zHLwdcCxow+w5mXG1Zuzwd80Gl3wEhGsDQsePQ+JAiQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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