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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18abc278fabcbed1b3e77c3bd2ffd6eebc7ab5c8bc79517f79c5f6c41c9e79be' 
  AND token = 'D3I5z1hMSCpoiAR8PQc7LYzPRM7KzOAR1xFF/QImOZ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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