SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '568b2f998341bd31d56cdde8d582cf3bf1865735d4fb2a65acc7dfca1be06549' 
  AND token = 'vMuTbMwXZf+WpoFzguR8cvzGIpyj3VQhMS9frZ3kcSg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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