SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b36d8498e2d00f769b0e6894e14097bfce53d985eb4af7a340b350f1483f4e55' 
  AND token = 'gFejrrnQSdprkJMueCj46AoRI7qij6jQlUl0pknffM8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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