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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '821dffda15d9d934202047f6672a3725710ec60bbeba834013b8091e935714ea' 
  AND token = '//M9Eu+Y0t4P8/fGSnwL4P/1ivJ9idjkDF1+igbMfb0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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