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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1717b6c18f2e1f395fe5047773ef71a04e281e710d4d3d4dd6da8e9d3952ac4' 
  AND token = 'd8u8B94lhTqI/DNiBoRVaqVMEcgB9uGxZ2wBAGytmiU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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