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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c6738f1f62ba78c233664cf76d1fb17faf9d74db8093db7dca9d637f92cfa3a' 
  AND token = 'jpxrgvWIHNlQmxH2jUtWOuRO6lgGm7osxE/LyqMNo1U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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