SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68fd4f6ca3e0e61931392024996c13bcbb2ff930d0e60587d5d337b74b3e9ab9' 
  AND token = 'oX6ggfcJ5hJuQSBnTSqxgQn+PuV6xUuWMGwITl2NT+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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