SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51186c9125afe2a71fc744cbb527cddae9705b2a010139cd8c64262d0336e785' 
  AND token = 'dJyf8U/m3Dog+obuxbQIMnFy49mcvM2OLeUBDZCDOOU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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