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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5156ab6dfe9b1997c8c80ca3f6985305e5fdd41c4f3b8d87ce07c1e9d0d80400' 
  AND token = '/IcAGI1b6f7TTBMw7wWcMuFidthQ0vAlTtQ9rvF+l9E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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