SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7cd836eddb08cd510d7d2a903fd7ca351658df4fe2f5c45923decffde89235b2' 
  AND token = 'iBOZDC6KzyfSCOW0ka0dJVhQBKbE040SCJA7imY6DDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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