SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1421c6cdd96488557a32f4c90bb480edeb1061e50d1c6964d09f7917f2a0e6ce' 
  AND token = 'K4I7wjK7pTEHXQ1JEOEDefWlUJioO3hFi8d/EcnVhi4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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