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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3920e36dbd05f5d77c45f8f2d6906aa31ef81ccf7cbf239f82204b5f78ba495' 
  AND token = 'XnI8uJkHQrvWZ4puNhACPyPIvWJHk1J5zSDElOhOIb0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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