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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b6dab6e81f379339ffe75dbc3ef92765952147916c064eee3dcdc99342fceaf7' 
  AND token = '810cyMchzgg5pHvBE+V5tRwbSm0t1GTD7vVduxl+IfI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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