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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '28124ea68ff249fdcfb9758d4c27c748b9c3c895f51fc0892ea68876095d1fa8' 
  AND token = '5elO8SmwmdW/UyKBTl/ni8CKDn1Ys4UUCNIMKQQoVkA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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