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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6df0a088ab08c91d111803b44d3282b7050538da261beb44c38af631ab61ed60' 
  AND token = 'QgMLQAJOlxSh8pjUO1AbteCc5oxFHg0BZPixnN7m5i8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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