SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cef15d6e8297b78fa64bc01a019159e8fa84c7132963438a17bac0be8663cf90' 
  AND token = 'uj0zRk720JHx+b/ngziGnlNNqs64stuA0AEDFcCPS9o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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