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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c57b8c6cde2748990fa3bc0f11f2c5a67b97d51acc4c1e38ad2bc3b15c668c9a' 
  AND token = '1AtCjz4pevI/nfWlVsuZ3GkHksr7nGWwztfPrNPCA/8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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