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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f6487dfe5519949d985f3cf5b91d3ec01fec60b65d244d2adf50b4c7b92d9812' 
  AND token = 'sEGf6/yvxBK5WUa1WWg9AWEpyY0cduahzdXjpcT7QTQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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