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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5ad5a7a49371a9afbc3d060f346e69073590fb4797ee5496dbf3b3cc96da3dd' 
  AND token = 'rPpAdHkzt3rjl2+BmeFSTWDA8+4lnL4IfTvzfWkGfMI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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