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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8dc62e04759e1e9bd6370789fd8142de52a0fca66b85b52a82d1e75db35ca79' 
  AND token = 'WDUuCMpAyfEQ9uWQxD9i4jtrd5aBUwm+2NLsGfzTnOQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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