SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6de850d0083ef7f4693038009f02b00e68060889229abb461508abfffb923350' 
  AND token = 'cmAo1b5C7bRgbu1jRTpG+nO164rK8G4KYI5JB0GMfeQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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