SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '208b6e5e159103b55e65ae0fa6394647102d47fdb97ed0506df70961c0adee3a' 
  AND token = 'iJig6Vj+ZVMywP8a9XRHxSGtYzV/uL3BmUbPKEQClrU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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