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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0a4d3e3a66cb471d93aa6d66cc85dc9dfee8c9e20a81bedaa06c9f15523bb749' 
  AND token = 'WEI4/mHSsqBU5lrKedoqpdawQ9LD1EafcDSo9xLXgd8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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