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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c83e8ecc6bd9a9b8b46e94409f0c8aff426c997128830272d6b36d618206ce03' 
  AND token = 'Uq/rkxRFZU80Trzh17KKOi67Dqv0GBO0JZiC84SbL60=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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