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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6e1618f4be52b25f2a675fd1e4ee95d17b735f682d0831bf6093eb5ca3bd76a' 
  AND token = 'c0hm5TEOZV5I4ceWvNmICF6OmBVFoY7C9GjXF+Hd2CQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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