SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3186e6879eaa27f10734db8f71b26d03e9118591cc289f0324d27b9586502599' 
  AND token = 'T0lCdkVdXH3vYlCryY1JghoeJ3mXlD4VAZMPVfntHgo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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