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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'defc3d206f11dd1884642d4183db0558eb1375b66b91a673314ec13548da00e2' 
  AND token = 'EByaShIGcTwLFg5eUrjt4Bse0mrALwhYLQG6V2jQCPs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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