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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '620b2f93c4966b8f2065a0493d112fcdaaada3c2c1352fcefc28697fe496b59d' 
  AND token = 'XxvCEaGQ9KEwEYaez4l9UeiVI/dzqyX/5JyhBdtWKaQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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