SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c8b4194165f3f25514427ea475e3ea43de1e7237a94e1bb3d3f8b990a3550e7' 
  AND token = 'WPapNbt30BwjRwxoeopuGqHJ3FMoWa7qmb83ZlIn2iI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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