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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9f869ae2a86ccfed374ad8afb0d55f35b89078f6a5a437cbfb3d8d0bd41acf37' 
  AND token = '4pQKdR3+Opyxc0F/4M8cedkhhUJQSRVpUSoCeV0QiJ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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