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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b258b7f2a534d7a5677374721d3afe665d1f3674e05480d6589c6710a32cee35' 
  AND token = 'bHH5n4+5hN5kmgXmHthyq8CaStETLSou8nAHy9+NY1M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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