SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b855d48cfb2c14f011ef3ecff54e809cc24483bd34122359bb2ff98a91b7a35' 
  AND token = 'XEogh94FTHPZCJI6GINAmdXk1JeE4e5/BfHQPaYf81A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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