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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d7d3af976a411d52ca00fdef0a4062518df84844c8b8a322625bf05abc14cd' 
  AND token = '65Qb0dvoMK7dMJI3UmB6DtrCu4mb9d5zYiQzyBTnQGI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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