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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'aa79a479fdd90fba57f90f69341d5b648a7f46fdc7cee470a1c289e57ecfa3df' 
  AND token = 'YdBAs4+oxq0bRu0azCYLW3QGBZ4C6Dstc+QYH4/6Ak8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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