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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8516176a9f04e3cbd3452bee387fbc32e39ef7d75e2a1b209aae9fcd2fb1e00' 
  AND token = '6n0iN69ZjtduV9+BJiAM0oFHTWbkSnMJ90yL4rA6acI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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