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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15bd8cd23e85be4b224d0cd1dd321f0d3e5ac25d51aaccff8bcdd505ac19b0d8' 
  AND token = '2gbeVbyWCQdYHVeJFZHgamycerLoMFqhrvTl2CI+Ndw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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