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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b18b2f9c8bbeae47f9e37e934bd23cb6e7faeda8a8989db1f9c0e0f8f1fb86c5' 
  AND token = 'R+x/+StSrypD6XSlQuc3bnqkK9z9l6ic58aoHRlFd7o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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