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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6fe804fe23e520028d2debfb34ea6f9025ee36d8370b5342d325b5fb0d668583' 
  AND token = 'gNVXLINXokN8kBHNUiggyYeDfySDGr5uR73v+gWGQBI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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