SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b647eab44b7964c14679f45da7f384a829b30f4a81e07123b7e9da7eace79554' 
  AND token = 'f0RvYCs+MP/cKglvfRdQt9XbVV+qJ0qmwMpdzZ3/Nk8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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