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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '676ee364015e1b3a3e689b9429deb7fb8f973539c9b6209f90edff5d7d2eef68' 
  AND token = 'QcBUN/Tt0rybAZYqlEbPJ3RycAcWlujtqq3LDj78Hy0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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