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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4918428a4595096769222f8e267e281f33b47983e602cc16c45b3e1a61681326' 
  AND token = 'U5PLzkEJMe69GcGutIwarHL1ODOjsUoqLlVan5NH/6o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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