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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b71d59c93cf4931ef275feec1f4d7ef29b0f22b50e0fd917eff58dc3bb8d6cf' 
  AND token = 'I5qms+0BF8z5d1C8KH/ptg17xz87uSqTstgLyMiQ1wQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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