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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15a6bda51f1dd8a4b87ac04b96554cd9d4dd804cdfbd0be558acb5e863bd23a6' 
  AND token = 'p30C4YBhUj9xz1JZx8Lh8imWKm4xyiISMbYQ0iuggZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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