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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ef8f01cf4550b890521febb3896e3e125fcf15f80d33d8234ccc9ab5536f899' 
  AND token = 'KUy7PNpzuEP4xCNAZYJGtHcZxcq+1oqjTeQd3WQKej8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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