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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b492cf63140d91565cb0c4541996ca816748bba5e52974ff5015c98b467c9b1b' 
  AND token = 'cArm0/F/UCO4lgR9dDu0WL9+wvbJVOJrmibZmgBfT0E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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