SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '521071fb87e5fa5fad95ebcac4e28b42534a1368b098463b4bcdef046179d0d1' 
  AND token = 'B7fqiPYDsEGupAjm1foMSd+zSdjTBxlOskVAE0/lup8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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