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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9400b1b85b15c7d79e69bd1e211bf1193adff847cf8cedb1a81a4f0b9284460' 
  AND token = 'D8qEJvfPY1h3UNaF6bgSz2n4azJbVwQGjt7QpwdU7Ow=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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