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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e2799ad2efee593ee6021ad1a460096cfdde5607634066741bb487ca273dd3ca' 
  AND token = 'Ms2Y0LWetyNkgG4Dg+ZziQk6z6NySHCR4aRy+/WHYwg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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