SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2a75d56286ee3db198a5c0cebbc473e30171c966694410ad820486d9de621a08' 
  AND token = 'ciNRi+RliPD7ZNFPug2jdfsnZCYLp5oWGzxqWLr9QdE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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