SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6d39e87e62bab9d458456011e112fede5f0c040908fb4e2eefaac437c3e49fa' 
  AND token = 'niK3c6M12tFDebwBCo9kLnfybuX+PXrV4NTY6RfcNoE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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