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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '299b600ebcb068f72eda0e3e6b06ccb0af9e1a0133fb28e23e9b60a31b3781aa' 
  AND token = '51cR3/vta4LWMARDbzTq8LmHjdgsHnGuGgE7b85vnQM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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