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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3321ef0973126f3ad340e969edced92a7ed321e8460c520ff843bc38b1604aa1' 
  AND token = '9f3oVeXoQP4MZblkaRei7oqHw+lYBa6sye8y3b0ifoI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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