SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56f3ee8f9a0b79f0a5bece7ae82436991484cce42d969c9a0aa494aae008490b' 
  AND token = 'akru+yuy9ZdIUAEfpuRVhgW0LvVACY/gZgPzQxyQwa4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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