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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '751ee3c3633c10b1d124c8e3b57c61301a1bd5b6ef0b39e6cee13b2718a0a1b5' 
  AND token = 'P1+K5EtJYFxrpYKeD7itPNIQzKTzT+Z++5eRECRtP9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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