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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3478c59629e46156bcea35ef1e5d559bc4b98533d0f958fc8056b8d80c21b41' 
  AND token = '8LqpM1FuSGDY/LiDiihCKxFTvxwQeqcxSGX/zajqyDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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