SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90b239fe2c2310a28d8585b472a8404110ee9e21ea56a5ad86be4ab3c03bc815' 
  AND token = 'spZBhi6D6zmEfcXskBoyhc4wygVQ+jAgPKy74PmLN90=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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